"you require the code to be under BSD"
This is actually a myth, we don't.
If you look through the Drizzle codebase you will note that very few files have BSD headers, and all that do?
They are a part of new systems that have been written since the fork of the project, and not all of these are BSD.
Why is this?
A large part of Drizzle is derived work from MySQL, and in all cases there we inherited its GPLv2 license on files. Bug fixes and code refactoring projects all fall under the umbrella of "derived work". In all of those cases the work was made under the GPL but no copyright assignment ever occurred. To understand ownership there you would need to look at the revision history to the code. We have never made any effort to track anything more then "where did the code come from".
I am a big opponent of copyright assignment in open source. How do you have an honest conversation with someone where you say "yes, I will need the work you did for free, to be assigned over to me, so that I can make money on it"?
Or better put:
"Here is $100 for the code you did, would you like some trinkets and beads to go along with that?"
We never did copyright assignment for Drizzle, and in no other project I have run personally have I ever done it. It is not a conversation I can have with a straight face with anyone. If you need commercial rights to your work and you want to do a true "quid pro quo"? License your code under the BSD license in the first place, that way both you and the contributor are on equal footing.
Does this mean we are a free for all when it comes to code? No, we track ownership. We know where every single line of code came from thanks to bazaar. If someone wanted to "poison" the codebase we would know exactly who that was. We would point the copyright owner to the offender, remove the code, and help with the prosecution of said individual. We have an active discussion going on at the moment about the future of our copyright headers, and one option we are considering is just replacing the copyright owner notice with a "Please see revision history for complete ownership information".
Are all of the files in Drizzle GPL? No, we do have some which are BSD.
I am a big fan of the BSD license and I typically suggest to developers that they use it for certain projects. As a license it links well with other code, and by establishing new plugins as BSD the original author can pull from any bug fixes that are made to the code. As an example Patrick Galbraith established the built in drivers that allows Drizzle to speak with Memcached. He has pulled code from the Drizzle driver and used that for his MySQL drivers. If those drivers had been done as GPL he would have not been able to pull code back into the MySQL Memcached drivers (which are BSD).
The GPL works just fine as the license for the kernel of Drizzle. I don't see that changing. In discussions with the other core authors, there has never been a push to "rewrite" the entire internals just to change the license. It is more work then it is worth, and it is not needed. The micro-kernel design means that going forward most of the work is pushed out to the libraries that link us to other systems. Work in the kernel is all about making those interfaces robust and creating more opportunity for plugin writers.
A final note on licensing and direction.
We never had any ambition to aim Drizzle at the deeply embedded market. Taking Drizzle, compiling it into a library, and linking it against another application is not a goal that the core team has ever had. If we had ever wanted to go into the world of deeply embedded databases we would have needed to have done code assignment or switched the entire license of the program.
In the deeply embedded world SQLite reigns supreme. SQLite does an awesome job in that space, and we see zero reasons to go head to head with it. If I needed a deeply embedded database I would just use SQLite, I wouldn't bother to write a new one.
Drizzle's core will stay GPL, and we continue to take contributions without code assignment. If you are a programmer I believe you can appreciate the merits of why we do this.
If you are a developer and you find yourself in the peculiar position of being asked to sign over your work? I would encourage you to take a hard look at why this is being asked, and see how comfortable you are with the value you are getting in return for your work.