Best Open Source Billing Tools for Subscription Monetization in 2026
Best Open Source Billing Tools for Subscription Monetization in 2026
Best Open Source Billing Tools for Subscription Monetization in 2026
Best Open Source Billing Tools for Subscription Monetization in 2026
Best Open Source Billing Tools for Subscription Monetization in 2026
Team Flexprice
Editorial
The best open source billing tools for subscription monetization in 2026 are the ones whose licence covers the features you picked them for, and four projects publish a billing engine you can actually run like Flexprice.
This piece is completely independent of Flexprice, and has been created after careful research and thought.
Key Takeaways
Flexprice publishes its whole engine under AGPL-3.0, with 4,302 stars and 493 forks per the GitHub API on 13 August 2026.
Lago Premium is quote-only and covers the customer portal, prepaid credits, entitlements and RBAC on self-hosted deployments as well as cloud, per its pricing page on 13 August 2026.
Kill Bill's FAQ puts raw event streaming in the paid Aviate add-on, not the Apache-2.0 core.
Chargebee bills 0.80% of monthly billing value, while Flexprice charges a flat fee per plan.
Which open source subscription billing tools compare best on the licence model?
The license model decides which features you can run, so read the LICENSE file and the pricing page together.
A permissive licence beside a quote-only premium edition can leave less running code than copyleft. Four projects publish an engine you can run, ordered below by how much works without a sales call.
Every figure I checked was live on 13 August 2026.
Tool | What sits behind a quote |
|---|---|
Flexprice | Nothing |
Lago | Portal, prepaid credits, entitlements, RBAC, SSO |
Kill Bill | Aviate tiers and support |
OpenMeter | Every price |
1. Flexprice, AGPL-3.0, nothing held back
Enterprise-grade usage based billing infrastructure for AI and SaaS teams.
The same engine runs in your own VPC on AWS, Azure or GCP, on-prem in any geography, or on our managed cloud, so usage and revenue data never has to reach a vendor.
Flexprice handles up to 1M events per second at under 60ms P99.
SOC 2 Type II certifies us as an operator, so a self-hosted build can't inherit it.
The best open source billing tools for subscription monetization in 2026 are the ones whose licence covers the features you picked them for, and four projects publish a billing engine you can actually run like Flexprice.
This piece is completely independent of Flexprice, and has been created after careful research and thought.
Key Takeaways
Flexprice publishes its whole engine under AGPL-3.0, with 4,302 stars and 493 forks per the GitHub API on 13 August 2026.
Lago Premium is quote-only and covers the customer portal, prepaid credits, entitlements and RBAC on self-hosted deployments as well as cloud, per its pricing page on 13 August 2026.
Kill Bill's FAQ puts raw event streaming in the paid Aviate add-on, not the Apache-2.0 core.
Chargebee bills 0.80% of monthly billing value, while Flexprice charges a flat fee per plan.
Which open source subscription billing tools compare best on the licence model?
The license model decides which features you can run, so read the LICENSE file and the pricing page together.
A permissive licence beside a quote-only premium edition can leave less running code than copyleft. Four projects publish an engine you can run, ordered below by how much works without a sales call.
Every figure I checked was live on 13 August 2026.
Tool | What sits behind a quote |
|---|---|
Flexprice | Nothing |
Lago | Portal, prepaid credits, entitlements, RBAC, SSO |
Kill Bill | Aviate tiers and support |
OpenMeter | Every price |
1. Flexprice, AGPL-3.0, nothing held back
Enterprise-grade usage based billing infrastructure for AI and SaaS teams.
The same engine runs in your own VPC on AWS, Azure or GCP, on-prem in any geography, or on our managed cloud, so usage and revenue data never has to reach a vendor.
Flexprice handles up to 1M events per second at under 60ms P99.
SOC 2 Type II certifies us as an operator, so a self-hosted build can't inherit it.
Use Flexprice’s On-Prem Feature to Simplify Your Billing Stack
Use Flexprice’s On-Prem Feature to Simplify Your Billing Stack
2. Lago, AGPL-3.0, with a quote-only premium tier
Meters and invoices in one platform, on a repo carrying 10,329 stars.
Lago Premium publishes no price and the only control is a contact form.
It covers the portal, prepaid credits, entitlements, RBAC and SSO, on self-hosted deployments as well as cloud, so the capabilities an enterprise contract needs sit behind a sales call.
Flexprice ships all five in the AGPL-3.0 build, next to parent-child accounts and contract versioning.
3. Kill Bill, Apache-2.0, with metering split from the core
Apache-2.0, Java, 5,682 stars, with a documented plugin framework.
Its own FAQ says the core records pre-aggregated usage per subscription, and raw event streaming arrives with the Aviate add-on, whose four tiers and three support tiers are all quote-only.
Metering the thing you bill on is therefore a paid upgrade.
Flexprice ingests raw events in the core engine at 60K+ per second, under AGPL-3.0.
4. OpenMeter, Apache-2.0, now shipped by Kong
Apache-2.0 on a repo with 2,194 stars, written in Go, and it runs the invoice lifecycle in the open build rather than metering alone.
Kong now ships it as "OpenMeter by Kong" and the cloud product goes by Konnect Metering and Billing.
No prices appear anywhere and no split between the open build and the cloud is published, so you can't cost it without contacting Kong.
Flexprice publishes every plan price and the revenue cap attached to it.
The hosted-only platforms, and why they aren't on the list
Orb, Metronome, m3ter and Chargebee publish client SDKs and no billing engine, and none names a self-hosting option.
Orb's three tiers are all custom-priced and Adyen's acquisition closed on 1 July 2026. Metronome's Starter bills 0.8% of billing volume plus $0.04 per 1,000 ingest events, and Stripe's acquisition completed in January 2026.
m3ter publishes no prices. Chargebee is hosted only at 0.80% of monthly billing value, so your bill grows with your revenue.
Flexprice charges a flat fee per plan and never a percentage, and none of these four can keep your usage data inside your own perimeter.
What does it cost to operate self hosted billing?
Self hosted billing costs nothing to licence and real money to run, and engineering time is the underestimated line. Whatever a project leaves out you operate yourself, and our open source billing software guide has the component list.
Cost line | Self-hosted | Flexprice managed |
|---|---|---|
Licence | $0 under AGPL-3.0 | Free, $500/mo or $1,000/mo, 20% off yearly |
Engineering time | 4 to 8 hours a week on ClickHouse alone, $1,600 to $4,800 a month, per Tinybird | Zero |
Self-hosting wins when your platform team already runs Kafka and a columnar store. It loses when billing has to be live this quarter.
Our pricing page has the managed side, and Segwise spent three weeks building credit-based pricing in-house before shipping it on Flexprice in three days.
Frequently asked questions
How do open source billing licence models differ in practice?
AGPL-3.0 and Apache-2.0 both let you run and modify the code. What bites is the part outside the repository, like quote-only Lago Premium, which applies to self-hosted deployments too, as of 13 August 2026.
Which open source billing tools include usage metering?
Flexprice meter inside the engine that invoices. Kill Bill's core takes pre-aggregated usage and needs a plugin or the paid Aviate add-on for raw events, per its own FAQ on 13 August 2026.
Where do open source subscription billing tools leave feature gaps?
The gaps surface after your first negotiated enterprise contract, not during metering. Four capabilities decide it:
Parent-child accounts rolling subsidiaries into one consolidated invoice
Ramped commitments with mid-cycle overages
Contract versioning with tracked history
Multi-currency across more than one gateway
All four ship in the Flexprice AGPL-3.0 build, next to RBAC and CRM sync, across Stripe, Razorpay, Moyasar and Nomod. SOC 2 Type II sits on the managed deployment, not on a build you host yourself.
Where should you start?
Run this on your shortlist:
Open each tool's LICENSE file and pricing page together, and mark which capabilities appear in both.
Price the operating side against what your platform team already runs.
Flexprice's billing engine sits at github.com/flexprice/flexprice, where Usage Metering starts.
2. Lago, AGPL-3.0, with a quote-only premium tier
Meters and invoices in one platform, on a repo carrying 10,329 stars.
Lago Premium publishes no price and the only control is a contact form.
It covers the portal, prepaid credits, entitlements, RBAC and SSO, on self-hosted deployments as well as cloud, so the capabilities an enterprise contract needs sit behind a sales call.
Flexprice ships all five in the AGPL-3.0 build, next to parent-child accounts and contract versioning.
3. Kill Bill, Apache-2.0, with metering split from the core
Apache-2.0, Java, 5,682 stars, with a documented plugin framework.
Its own FAQ says the core records pre-aggregated usage per subscription, and raw event streaming arrives with the Aviate add-on, whose four tiers and three support tiers are all quote-only.
Metering the thing you bill on is therefore a paid upgrade.
Flexprice ingests raw events in the core engine at 60K+ per second, under AGPL-3.0.
4. OpenMeter, Apache-2.0, now shipped by Kong
Apache-2.0 on a repo with 2,194 stars, written in Go, and it runs the invoice lifecycle in the open build rather than metering alone.
Kong now ships it as "OpenMeter by Kong" and the cloud product goes by Konnect Metering and Billing.
No prices appear anywhere and no split between the open build and the cloud is published, so you can't cost it without contacting Kong.
Flexprice publishes every plan price and the revenue cap attached to it.
The hosted-only platforms, and why they aren't on the list
Orb, Metronome, m3ter and Chargebee publish client SDKs and no billing engine, and none names a self-hosting option.
Orb's three tiers are all custom-priced and Adyen's acquisition closed on 1 July 2026. Metronome's Starter bills 0.8% of billing volume plus $0.04 per 1,000 ingest events, and Stripe's acquisition completed in January 2026.
m3ter publishes no prices. Chargebee is hosted only at 0.80% of monthly billing value, so your bill grows with your revenue.
Flexprice charges a flat fee per plan and never a percentage, and none of these four can keep your usage data inside your own perimeter.
What does it cost to operate self hosted billing?
Self hosted billing costs nothing to licence and real money to run, and engineering time is the underestimated line. Whatever a project leaves out you operate yourself, and our open source billing software guide has the component list.
Cost line | Self-hosted | Flexprice managed |
|---|---|---|
Licence | $0 under AGPL-3.0 | Free, $500/mo or $1,000/mo, 20% off yearly |
Engineering time | 4 to 8 hours a week on ClickHouse alone, $1,600 to $4,800 a month, per Tinybird | Zero |
Self-hosting wins when your platform team already runs Kafka and a columnar store. It loses when billing has to be live this quarter.
Our pricing page has the managed side, and Segwise spent three weeks building credit-based pricing in-house before shipping it on Flexprice in three days.
Frequently asked questions
How do open source billing licence models differ in practice?
AGPL-3.0 and Apache-2.0 both let you run and modify the code. What bites is the part outside the repository, like quote-only Lago Premium, which applies to self-hosted deployments too, as of 13 August 2026.
Which open source billing tools include usage metering?
Flexprice meter inside the engine that invoices. Kill Bill's core takes pre-aggregated usage and needs a plugin or the paid Aviate add-on for raw events, per its own FAQ on 13 August 2026.
Where do open source subscription billing tools leave feature gaps?
The gaps surface after your first negotiated enterprise contract, not during metering. Four capabilities decide it:
Parent-child accounts rolling subsidiaries into one consolidated invoice
Ramped commitments with mid-cycle overages
Contract versioning with tracked history
Multi-currency across more than one gateway
All four ship in the Flexprice AGPL-3.0 build, next to RBAC and CRM sync, across Stripe, Razorpay, Moyasar and Nomod. SOC 2 Type II sits on the managed deployment, not on a build you host yourself.
Where should you start?
Run this on your shortlist:
Open each tool's LICENSE file and pricing page together, and mark which capabilities appear in both.
Price the operating side against what your platform team already runs.
Flexprice's billing engine sits at github.com/flexprice/flexprice, where Usage Metering starts.
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