MySql wants everyone to become a partner, and when you are one, you should sell your customers commercial licenses of the mysql provider. That's their plan. If you realize that their provider costs more than 200 euro/developer, you quickly realize this isn't really something to do.
It's not the sourcecode of our designer: if we purchase a license of their provider, we can ship our stuff closed-source, no problem.
The problem is with our customers using our DQE: they have to use a version of their mysql provider in that case, which is either GPL or commercial. If the customer uses the GPL version and distributes the app, the customer also has to distribute the sourcecode of our runtimes as the DQE links to the provider.
I.o.w. a lame situation. It's exactly as the forum poster explains in the post you link to: they should release their connector as LGPL, and be done with it. However, that would kill off the business of everyone having to pay a lot of money to even connect to their bad excuse for a database.
Core lab has different issues, though their code is relatively cheap. I have no idea how their controls behave in 2008, they seem to be pretty fond of their entity framework provider so I guess it works OK. Their provider works OK with our code so you should be in safe waters.
We contacted MySql a couple of times to learn more about if we could solve this crap for our customers. We deliberately asked for their LEGAL stance about the situation I described above: where our customers use the GPL provider and distribute our code.
We never got an answer to that question, we only were told a couple of times to become partner and sell these provider licenses at a discount price.... It's the same dumb story Reggie tries to sell the world in that thread. You'd think that a person who works on a connector understands that if people can't use a connector, they can't connect to your database and probably will use another brand/type...
We have no interest in becoming anyone's partner to allow my customers to connect to a database. If MySql doesn't want us to use their connector, it's their loss. Maybe, with Sun now in control, this will change over time, though I have my doubts.