The Rise of "Source Available" vs True Open Source
The Rise of "Source Available" vs True Open Source
You can see the code. You can self-host it. But is it open source? The rise of "source available" licenses is blurring the line — and it matters more than you think.
The Spectrum
| Category | Can Read Code | Can Modify | Can Distribute | Can Compete | Examples |
|---|---|---|---|---|---|
| Proprietary | ❌ | ❌ | ❌ | ❌ | Slack, Notion |
| Source Available | ✅ | ✅ (limited) | ⚠️ (restrictions) | ❌ | Sentry (BSL), MongoDB (SSPL) |
| Open Source (copyleft) | ✅ | ✅ | ✅ (share alike) | ✅ | Mattermost (AGPL), Linux (GPL) |
| Open Source (permissive) | ✅ | ✅ | ✅ | ✅ | React (MIT), Kubernetes (Apache) |
What Makes Something "True" Open Source?
The Open Source Initiative (OSI) defines open source through the Open Source Definition. Key requirements:
- Free redistribution — Anyone can share it
- Source code available — Must include or make available
- Derived works allowed — Can modify and distribute modifications
- No discrimination — Can't restrict who uses it or for what purpose
- No restriction on other software — Can't require that other software also be open
OSI-Approved vs Not
| License | OSI-Approved | Type |
|---|---|---|
| MIT | ✅ | Open Source |
| Apache-2.0 | ✅ | Open Source |
| GPL-3.0 | ✅ | Open Source |
| AGPL-3.0 | ✅ | Open Source |
| BSL-1.1 | ❌ | Source Available |
| SSPL | ❌ | Source Available |
| Elastic License 2.0 | ❌ | Source Available |
| Confluent Community License | ❌ | Source Available |
Why Companies Are Choosing Source Available
The Timeline
| Year | Company | Change | Reason |
|---|---|---|---|
| 2018 | MongoDB | AGPL → SSPL | AWS offering managed MongoDB |
| 2019 | Elastic | Apache → SSPL + Elastic License | AWS Elasticsearch Service |
| 2021 | Grafana | Apache → AGPL | Preemptive protection |
| 2023 | HashiCorp | MPL → BSL | "Vendors taking without contributing" |
| 2023 | Sentry | BSL | Sustainable business protection |
| 2024 | Redis | BSD → RSALv2 + SSPL | Cloud provider competition |
| 2024 | Terraform | BSL | (continued from HashiCorp change) |
The Pattern
1. Company creates open source tool (MIT/Apache)
2. Tool becomes popular
3. Cloud providers offer managed version
4. Company can't compete with cloud providers' scale
5. Company changes license to restrict cloud providers
The Business Source License (BSL) Explained
BSL is the most common source-available license. Here's how it works:
Years 1-3: Source Available
- You can read, modify, and self-host
- You CANNOT offer it as a competing service
- The "Additional Use Grant" defines what's allowed
Year 4+: Becomes Open Source
- Automatically converts to Apache-2.0 (or similar)
- All restrictions lifted
BSL in Practice
| What You Can Do | What You Can't Do |
|---|---|
| Self-host for your company | Offer a competing managed service |
| Modify the code | Sell hosted access to the software |
| Contribute patches | Build a SaaS product using it as core |
| Use internally (any purpose) | Resell as-is |
Who Uses BSL
| Project | BSL Since | Converts To | Additional Grant |
|---|---|---|---|
| Sentry | Launch | Apache-2.0 | Can use for internal business |
| CockroachDB | 2019 | Apache-2.0 | Non-commercial use |
| MariaDB MaxScale | 2017 | GPL | Non-production use |
| Outline | Recent | Apache-2.0 | Self-hosting for any purpose |
Does It Matter for Self-Hosters?
For Most Users: No
If you're self-hosting for your team or company:
| Question | BSL Answer | True OSS Answer |
|---|---|---|
| Can I self-host? | ✅ Yes | ✅ Yes |
| Can I modify the code? | ✅ Yes | ✅ Yes |
| Can I use for my business? | ✅ Yes | ✅ Yes |
| Can I see the source code? | ✅ Yes | ✅ Yes |
| Is it free? | ✅ Yes | ✅ Yes |
When It Does Matter
| Situation | Impact |
|---|---|
| You want to offer it as a managed service | ❌ BSL won't allow this |
| You want to fork and build a competing product | ❌ BSL won't allow this |
| You want to embed it in commercial software | ⚠️ Depends on the Additional Use Grant |
| You want long-term guarantee of openness | ⚠️ BSL converts in 3-4 years, but company can change terms |
| You contribute code | ⚠️ Your contribution is under BSL, not true OSS |
The Community Response
Forks
When companies changed licenses, the community responded with forks:
| Original | License Change | Fork | Fork License |
|---|---|---|---|
| Elasticsearch | → SSPL | OpenSearch (AWS) | Apache-2.0 |
| Terraform | → BSL | OpenTofu (Linux Foundation) | MPL-2.0 |
| Redis | → RSALv2 + SSPL | Valkey (Linux Foundation) | BSD-3 |
Result: The community now has true open source alternatives, but the ecosystem is split.
The Debate
Pro Source Available:
"We gave away our software for free. AWS made billions offering it as a service and contributed nothing back. BSL lets us survive while keeping the code visible."
Pro True Open Source:
"If you benefited from open source community contributions under an open license, changing the license is a betrayal of trust. Fork it."
The Pragmatist:
"I just want to self-host software that works. I don't care about the license as long as I can run it on my server."
How to Evaluate Licenses as a User
Quick Decision Framework
| Your Use Case | MIT/Apache | AGPL | BSL | SSPL |
|---|---|---|---|---|
| Self-host for team | ✅ | ✅ | ✅ | ✅ |
| Modify for internal use | ✅ | ✅ | ✅ | ✅ |
| Offer as managed service | ✅ | Share mods | ❌ | Share everything |
| Embed in proprietary product | ✅ | Consult lawyer | Depends | ❌ |
| Fork and compete | ✅ | ✅ (share alike) | ❌ | ❌ |
| Long-term freedom guarantee | ✅ | ✅ | ⚠️ (converts eventually) | ⚠️ |
Our Recommendation
- Prefer true open source (MIT, Apache, GPL, AGPL) when alternatives exist
- BSL is acceptable for self-hosting — it works the same as OSS for most users
- Be cautious of SSPL — the restrictions are broad and vague
- Always check the license before building on top of a project
The Bottom Line
"Source available" licenses like BSL are a pragmatic response to cloud providers freeloading on open source. For self-hosters, the practical difference is minimal — you can still see the code, modify it, and run it.
But the philosophical difference matters: true open source guarantees your freedom to use software however you want. Source available gives you most of those freedoms with a business-protection carve-out.
When choosing tools for your stack, prioritize true open source where possible. But don't let a BSL license stop you from using a great tool — especially when it converts to open source after 3-4 years.
Check the license of every open source alternative at OSSAlt.