There is now one fork and one major branch of MySQL now that I will mention, both are exciting projects-- and neither of them is coming from official MySQL/Sun:
(The order of these is strictly alphabetic and not priority!)
Drizzle -- https://launchpad.net/drizzle
Drizzle a fork of MySQL 6.0, is a project started by Brian Aker and team of Monty Taylor, Jay Pipes, Stewart Smith and others, to produce a "database optimized for Cloud and Net applications. It is being designed for massive concurrency on modern multi-cpu/core architecture". I myself have made some attempts with my busy book schedule to help out on this project and am in the process of working on DBD::drizzle. This team is working night and day on this project. It should be also understood that this project is sanctioned and supported by Sun.
MariaDB -- http://askmonty.org/wiki/index.php/Mari
"MariaDB is a community developed branch of the MySQL database that uses the Maria engine by default". This is the branch that Monty and several core Maria Developers are working on. The intent of this branch is to keep up with MySQL development, maintain user compatibility, but with more features. With Monty at the help, I feel very happy about this. I will be contributing to this project and intend on incorporating FederatedX into it as soon as this book is done!
I want to work on both projects - if I write my code intelligently, it can run with both.
So, what about MySQL/Sun? What are they doing with the source they own? I know that I've had frustrations with things like FederatedX not working when something in the server is changed. Also, Federated development was ceased a while back so the responsibility is for me to keep Federated moving forward-- this I can do with Drizzle and MariaDB. This is important because a lot of people use Federated and want to see bugs fixed and features added. I don't know if I will get the same ability to work with the internal MySQL/Sun team.
My question is then: what is the official tree? The project lead is Monty, and if he is now saying "MariaDB" is the official tree. Does that mean that the tree at Sun is now dead? Open source projects usually have their souls found in whoever personally leads the project, not in who owns the copyright of the name. Monty and Brian certainly are open source leaders, so my inclination is to follow them. This is not a slight to MySQL/Sun either, but a question that me as a both a user and developer of MySQL, as well as a former employee and team member of the MySQL development team.