Since 11/2016 stracker and ptracker are available under terms of the GPL. You can access the source code using git:
git clone http://n-e-y-s.de/git/sptracker.git
Please read the documents README.txt and LICENSE.txt. If you like to contribute to the project, you are very welcome. I'd like to avoid forks of stracker and ptracker, if possible. So please contact me before you create a fork; maybe we can find a solution to incorporate changes in the trunk.
Note that at the time being, the git repository is a clone of my private svn repository and it is set up read-only, I am currently the only user with write access to the repository. Depending on the responses from the community, I might change that in the future, so the git repository might get the development master and people wishing to contribute get write access to the repository.
I'm looking forward to get comments from the community regarding this decision. As usual you can contact me on the AC forums (user never_ear_yellow_snow1) or on racedepartment (user Neys).