I think they pledged to free it when they stop working on it, but that's about it. One of the developers posted a message[1] on their forums when they were asked about it, and their stance was pretty much "we don't see a good enough value in open sourcing our software". I am unaware of further developments.

[1] https://forum.obsidian.md/t/open-sourcing-of-obsidian/1515/1...