Documentation for Subversion (sometimes referred to as "SVN") is available here.
Anonymous Subversion Access
This project's SVN repository can be checked out through anonymous access with the following command(s).
svn checkout svn://svn.r-forge.r-project.org/svnroot/lme4/
Developer Subversion Access via SSH
Only project developers can access the SVN tree via this method. SSH must be installed on your client machine. Substitute developername with the proper values. Enter your site password when prompted.
svn checkout svn+ssh://firstname.lastname@example.org/svnroot/lme4/
Data about current and past states of the repository
Subversion Repository Browser
Browsing the Subversion tree gives you a view into the current status of this project's code. You may also view the complete histories of any file in the repository.