So far the reaction to Sun Microsystems' acquisition of MySQL AB has been mixed. Sun's Chief Open Source Officer, Simon Phipps, thinks it's great, of course. In a Computerworld piece, Phipps says:

I've yet to find anybody who loses because of this deal. Some [critics] will say its subtractive, but it isn't. It's an additive move. I've heard some people say that maybe we're going to force people to use Solaris, but that would be a crazy thing for us to do. MySQL is in safe hands.

On the other hand, the idea that Sun would "force people to use Solaris" apparently wasn't just pulled out of thin air. They have used similar tactics in the past. Also quoted in the Computerworld article, The Kusnetsky Group principal Dan Kusnetsky notes:

If Sun uses this strategy with MySQL, there are a significant number of open-source database competitors, PostgreSQL for instance, that customers can migrate to. If they [force a migration to Solaris] with MySQL, Sun will gain a great deal of ill will from this community and probably lose customers for MySQL.

Pund-IT principal analyst Charles King likens a proprietary company's purchase of an open source company with a community behind it to "buying an historic home in a small town." He says:

You may think that you own it, but a lot of people in the neighborhood have a very strong attachment or even a deeper attachment than you do.

It seems that everything depends on what Sun does with MySQL. Illuminata's Gordon Haff, for one, doesn't see a problem:

To the degree that there will be increasing [economic and sales] resources to MySQL ... in that sense, I think it's good for the MySQL community. I think it's fairly clear that [MySQL] wasn't a company that was rolling in dough, and I think that becoming a part of Sun opens a lot of opportunities ... that could really help the project.