Getting the source
Vanilla up-stream
See the tools project for build guides for various platforms.
You might be interested particulary in the Get the source code section in the build guide (for Linux, but it is quite similar for all the platforms).
export 'CVSROOT=:pserver:anoncvs@anoncvs.services.openoffice.org:/cvs' cvs login (CVS password: anoncvs) cvs co -r <milestone> OpenOffice2
The tool to browse project source code online has some additional hints.
If you want just to test development releases, you can download already compiled builds from [1]. List of available Mac builds is in Mac OS X Development Builds.
ooo-build
There are loads of versions of OO.o, and several choices of branch, with multiple outstanding patch sets. I recommend you build from up-stream CVS HEAD milestones (SRC680 milestones), with patch sets to make them easier to build from [2]
The very latest ooo-build (a small ~1.5Mb build wrapper) can be got from CVS thus:
export CVSROOT=':pserver:anonymous@anoncvs.gnome.org:/cvs/gnome' cvs login cvs -z3 checkout -P ooo-build
Note: You are going to need to download an additional ~150Mb of compressed source, and have ~3Gb of space to unpack and build it in.
