The TM5 source code is available for all researchers in the TM5 Usergroup.
If you're institute is interested in joining the user group in long term development of the model, you might contact Maarten Krol to share your ideas on cooperation.
The source code of TM5 is developped with the aid of the version control system CVS. For an introduction to cvs, the codex cvs-server, and information on how to obtain an account, see the codex homepage:
http://www.knmi.nl/samenw/codex
An up-to-date version of the model can be extracted via:
cvs -d :ext:yourname@codex.knmi.nl:/cvs/TM checkout TM5