Documentation for Subversion (sometimes referred to as "SVN") is available here.
Anonymous Subversion Access
This tool/resource group's SVN repository can be checked out through anonymous access with the following command(s).
svn --username anonymous --password anonymous checkout https://www.nitrc.org/svn/ahead
Developer Subversion Access via DAV
Only tool/resource developers can access the SVN tree via this method. Substitute developername with the proper values. Enter your site password when prompted.
svn --username developername checkout https://www.nitrc.org/svn/ahead