MySQL is ... free for personal use.

Slight correction. MySQL is actually free for nearly any use. The GPL does not allow restrictions to be placed on what a product is used for. The "commercial license" is for folks who want to do stuff the GPL explicitly disallows -- namely, close the source. As long as one doesn't plan on distributing MySQL closed source, there's almost nothing you can't do with it (in terms of allowed usage; I'm not talking about competency as a database engine, which is something I'm not the best judge of).