The process of adding users to SVN has not been well understood among the development team. This page provides instructions for the task.
It's a three step process.
First, ssh into the OpenMx server.
Second, add the new SVN user to the apache authentication list:
sudo htdigest /var/openmx/passwd/.htpasswd-digest OpenMx <username>
Third, add the new user to the dev group in /var/openmx/passwd/svnusers.conf (by adding their user name to the end of the dev= line) to authorize them with write access to the svn repo.
For the first step, you'll need an account on the OpenMx server. For the latter two steps, that account will require sudoer access. The new SVN user does not need an account on the OpenMx server, but the person who adds the new SVN user must have an account with sudoer access on the OpenMx server.