Did you know that you can checkout repositories from github.com via svn?
svn checkout http://github.com/mathjax/MathJax/trunk MathJax
You can run all svn commands on it.
svn status -u
To check for updates. If updates are available, run
to update to the current release version.
This gets you the most recently released version of MathJax. Older releases are available in "branches" named by the version number; e.g., v2.5-latest. If you prefer to use one of the older releases, then use
svn checkout https://github.com/mathjax/MathJax/branches/[name] MathJax
where [name] is replaced by the name of the branch you want to check out. The branch names can be found on the GitHub MathJax page under the branches tab.