Question 1

What's the difference between "open source" and "source-available" here?

Accepted Answer

Open source means an OSI-approved license — MIT, Apache 2.0, GPL, and similar — so you can run, modify, and redistribute it freely. Source-available means the code is visible but under a license, like BSL or a custom "fair source" license, that restricts commercial use or redistribution. We label each listing with which one it actually is, since the distinction has real licensing consequences.

Question 2

Is "open source" the same as "free"?

Accepted Answer

Not necessarily. The license is free to use in the sense that you can self-host at no licensing cost, but most projects here also sell a hosted or managed version, and self-hosting has its own real cost in infrastructure and maintenance time. Check each listing for what's actually free versus what's the paid tier.

Question 3

How do you judge whether a project is actively maintained versus abandoned?

Accepted Answer

Recent commit activity, release cadence, and issue response time — not star count. A project with a large star count from years ago can be effectively dead, while a smaller, newer one might be actively maintained. Verify directly on the project's repository before depending on it.

Time-Series Databases

Already pay for some of these?

Frequently asked questions