"some were paying for non-gpl'd versions of the code to integrate/resell in their products"
If that's what they need, perhaps to migrate their products to a BSD-licensed RDBMS like PostgreSQL. Or to a public-domain one like SQLite. Or a fully proprietary one. It's their software and, since, they have already licensed it as proprietary, their users were already robbed the freedoms GPL'ed MySQL would provide.
As it is now, those companies have licenses for specific versions. If they didn't get permanent unrevokable licenses and were happy with the cheaper ones they got, well... Phineas Barnum would be happy to use them as examples.
"whether this is fair is up for debate"
If handing over copyright is too expensive, companies are always free not to contribute or not to use Asterisk at all. They will, however, have to compete with other companies who do. Economics will dictate who wins.
"(and is partly why many users hate gpl software, preferring more "open" licenses like bsd/isc)"
The only freedom GPL denies a developer is to close up software that was once free. The only freedom the allegedly "more open" licenses give developers is to deny freedoms to their users. For the users (and software freedom is about them), those licenses give nothing.
But we are drifting from the original topic.
The topic is that MySQL is Oracle-proof and doesn't need saving the same way other GPL'ed products don't need saving. They are either good - and thus worthy of surviving - or bad - and thus will die natural deaths.
Many people have emotional attachment to their software. I must confess I am thinking and rethinking moving from Linux to OpenSolaris for much too long to explain it in strictly rational terms. I will miss it when Linux dies, but, by then, I expect GNU/HURD to run nicely on my 64-core ARM-based netbook. Or, at least, ZFS to be under GPLv3.