[joev]

I would argue that avoiding vendor lock out is a major reason Open Software exists: with an OS database, nobody can tell you that you can no longer use the DB software unless you pay the proper licensing and maintenance fees.

You'll be locked into a particular database vendor anyway: it's no harder to migrate away from MySQL that it would be to migrate away from DB2. It just so happens that the open source "vendors" don't charge licensing fees, and if things go way off the rails (community implosion, commercial "takeover" of the primary contributors, etc), at least you'll have access to the source so you can run your app on it for as long as it makes sense to do so.