http://www.bitkeeper.com/Hosted.Downloading.html
To download the falcon tree grab the client and then do the following to grab the falcon source:
bkf clone bk://mysql.bkbits.net:8080/mysql-5.2-falcon mysql-5.2-falcon
The BUILD directory has a number of our build scripts in it that we use to build binaries, so you may want to consider looking in the directory and executing the appropriate script ( I use compile-amd64- debug-falcon).