I think the fact he had to be told this by the board is more telling here. It's pretty obvious that YC was told about Altman becoming CEO of the for-profit Open

I think the fact he had to be told this by the board is more telling here. It's pretty obvious that YC was told about Altman becoming CEO of the for-profit OpenAI at the same time everyone else was told about it. Effectively, they gave him an ultimatum: stay at YC and drop that CEO offer or leave. Sure, it's dressed up in nicer words to protect Altman's dignity (which is fine, in terms of "this is bad" it's pretty low, so preserving his dignity makes sense), but that's still what it is. The ultimatum is obviously not a realistic one - be beholden to the board or become your own chief while it's blatantly clear where his ambitions lie, so effectively it's a firing.