I think posthog is one of these businesses where the COSS model does not work well.

COSS works well when there is a large distribution advantage of being OSS. This could be bacuse a large portion of users (need to) self-host the solution. This is true for databases, people will always need to self-host dbs (e.g. as part of their docker compose in dev, etc...). These people are also hard core engineers that will 1) talk about the db and 2) contribute to the project. So an OSS db have a large network effects and distribution advantage.

Posthog had a distribution advantage from OSS in their beginnings -- their beachhead was the self-hosting oss community. Now, it does not add much value -- It's unlikely Github adds much for their distribution. So, it does not make sense for them to do much more than just maintain it lightly. In fact, they try to push you from self-hosting by having great free tiers and startup programs.