Os X 10.5 comes with svn 1.4.4 preinstalled, but you might want to upgrade to the latest 1.6.2 for many reasons.
I needed the upgrade to run subclipse 1.4.x for flex builder 3. The best instruction I found on how to do this was here.
in a nutshell
1) download the universal subversion 1.6.2 binaries for mac from here : http://www.open.collab.net/downloads/community/
2) open terminal and type this : echo ‘export PATH=”/opt/subversion/bin:$PATH”‘ >> ~/.bash_profile
3) restart terminal
4) tpe svn –version and make sure you see :
—> svn 1.6.2