First, thanks for replying. But, I'll note you didn't answer my question, which is about the future of the current open source codebase. Knowing that you haven't changed the license on such code yet is great, but that doesn't speak to the future direction for that codebase.
EDIT: I just saw this reply to another child, which addresses this concern for the core timescale, I think! [0]
To be clear, I don't think the license change as described is a blocker for my org, given their use case. Indeed, it may be an near term win, as they will likely be able to take advantage of the new features that you are placing under this license.
That said, I always prefer open source code that I can modify myself. Open source licenses guarantee that the code can't be "taken away" from me, that I can integrate a technology without concerns for the sands shifting under me. If a company goes away, I and others can keep on working on it, and it can live on even if the original authors decide to no longer maintain it.
So, as an example: say Timescale changes the license of all its code under this new license tomorrow, then happily adds features and changes some fundamental things over the next few years, and then is bought by Oracle, who decides to take it fully proprietary under a new license that is more restrictive than the TSL license. This would make a fork unlikely or at least very difficult to get going!
[0] https://news.ycombinator.com/item?id=23276614