On the contrary Qt changed the license from GPL to LGPL what definitely helped the proliferation (and the survival after the Nokia disaster).
MySQL ... well moving this to AGPL would give MariaDB the final push it needs (if it still needs one). So they just let it rot.
Too bad there was no equivalent project for BerkeleyDB.
Also, a relatively restrictive (not BSD!) license has been a feature of Berkeley DB for a while:
> Tupl is a high-performance, concurrent, transactional, scalable, low-level database. Intended to replace BerkeleyDB, Tupl supports true record-level locking. Unlike BerkeleyDB-JE, Tupl doesn't suffer from garbage collection pauses with very large databases. Tupl also includes support for cursors, upgradable locks, deadlock detection, hot backups, striped files, encryption, nested transaction scopes, and direct lock control.
That's always been one of the ways to make money from free software. Mysql did the same thing, and I think Qt did as well at some point in its history. If I recall correctly, even RMS sort of approves of it.
Downvoters: go read some history, there's nothing factually incorrect in what I wrote above. The bozo proliferation seems to continue unabated here:-(
Here's RMS himself: http://www.fsf.org/blogs/rms/selling-exceptions