URL to build from is: http://svn.code.sf.net/p/firebird/code/firebird/tags/T3_0_0_Alpha1/.

Roadmap was also updated

http://www.firebirdsql.org/en/roadmap/

For testing you can use the pre alpha snapshots For Linux:

http://web.firebirdsql.org/downloads/snapshot_builds/linux/fb3.0/

and Windows:

http://web.firebirdsql.org/downloads/snapshot_builds/win/3.0/