If you want to build Subversion from a source release:
Download the latest tarball distribution from the Source Releases Area.
Windows users should download .zip files. For all other operating
systems, download .tar.gz or .tar.bz2 files.
Build and install it according to the instructions in the INSTALL file in the top level of the distribution. You will end up with a 'svn' binary in the subversion/clients/cmdline/ directory (or installed in /usr/local/bin/, if you ran 'make install'.)
Now you have the latest released version of Subversion installed. Read the Subversion Book to learn how to use Subversion, and to see how it differs from CVS.
If you want stability, you can stop here, and just upgrade as new releases come out. If you prefer to stay current with Subversion development, then use your newly-installed Subversion client to check out a working copy of the master sources:
$ svn co http://svn.collab.net/repos/svn/trunk subversion
That will get you a new working copy directory named
subversion/, containing the latest sources. (If you're
behind a proxy or have problems with the checkout, see the proxy faq.) Read the INSTALL file
for instructions on building in the working copy, which differs
slightly from building a released tarball.
See the Warnings and Inconveniences Page for the most annoying bugs and their workarounds; see the Issue Tracker for a complete list of known bugs, and instructions on filing new bugs.
To contribute to Subversion:
Join the developer community mailing lists: (see the Mailing Lists page.)
The Subversion project more-or-less abides by the guidelines used by the Apache APR project. Please review these.
After checking out a copy of the source as described above, read the file HACKING at the top of the tree. It describes coding and logging conventions, as well as how to build from a working copy.