You need to have the appropriate tools to download the code from the repository. Once the tools are installed:
The OTRS framework and some additional modules are available on github
There you will also find checkout instructions as well as a repository
Currently, a number of OTRS extension modules are still available via
CVS only. A migration to git is planned.
Login to the CVS with:
cvs -d :pserver:email@example.com:/home/cvs login
password is: cvs
To check out the 'HEAD', which is the current version in development
(experts and adventurous individuals recommended only):
cvs -z3 -d :pserver:firstname.lastname@example.org:/home/cvs co modulename
Checking out of a specific OTRS version can be done by using a release tag:
cvs -z3 -d :pserver:email@example.com:/home/cvs co -r rel-3_1
A web viewer allows you to browse the repository and compare file revisions in CVS.