Yes, our offering is of the "open core" nature, although our non-open-source code is covered under the Timescale License (source available, free). For most "open core" companies, this latter part is instead closed-source and paid, hence this terminology also leads to confusion :)

Anyway, here's the link to license pointers in github, and you can find all code there:

https://github.com/timescale/timescaledb/blob/master/LICENSE

    Source code in this repository is variously licensed under the Apache License Version 2.0, an Apache compatible license, or the Timescale License.

    All source code should have information at the beginning of its respective file which specifies its licensing information.

    * Outside of the "tsl" directory, source code in a given file is licensed under the Apache License Version 2.0, unless otherwise noted (e.g., an Apache-compatible license).

    * Within the "tsl" folder, source code in a given file is licensed under the Timescale License, unless otherwise noted.

    When built, separate shared object files are generated for the Apache-licensed source code and the Timescale-licensed source code. The shared object binaries that contain `-tsl` in their name are licensed under the Timescale License.