Working With the Sources
Obtaining the code
Sources for the release that is current today sit on the download page. Snapshots belonging to older releases and to beta builds are kept in the download archives.
The other route is a checkout from the project's Subversion repository, reachable at https://svn.filezilla-project.org/svn/FileZilla3
Whoever wants the freshest state of the code takes the development trunk:
svn co https://svn.filezilla-project.org/svn/FileZilla3/trunk filezilla
Each past release carries its own tag, so grabbing, say, the tree behind version 3.0.8-rc1 looks like this:
svn co https://svn.filezilla-project.org/svn/FileZilla3/tags/3.0.8-rc1 filezilla-3.0.8-rc1
If you would rather just look around, the repository can be browsed in a web page.
Building it yourself
Step-by-step build notes are kept in the wiki.