Mysql support is not implemented at the moment. If there's someone paying for the development we could have it. You're of course also free to contribute it yourself to the open source version, then it wouldn't need to be part of the commercial version.
Not OP, but it sounds like MySQL support isn't out yet. So I think the business plan can help them get paid to implement it. No clue if that means the FOSS version would receive those upstream changes once it's done.
Some more background on why IHP has a paid variant can be found here: https://ihp.digitallyinduced.com/blog/6392ad84-e96a-46ce-9ab...