What measures can I take to safeguard the source code of my django site from others?
If someone has the privileges to access anything/anywhere on the server you can't do much, because what you can do others can do too, you can try some way of obfuscation but that will not work. Only solution is NOT to use such shared repository.
Edit: options

Keep working with shared repository if your data is not very sensitive
Use dedicated hosting from companies like rack-space etc
Use AWS to run your own instance
Use google-app-engine server but that may require a DB change
Run your own server (most secure)
I have picked up python/django just barely a year. Deployment of django site is still a subject that I have many questions about, though I have successfully manual deployed my site. One of my biggest questions around deployment is what measures can I take to safeguard the source code of my apps, including passwords in django's setting.py, from others, especially when my site runs on a virtual hosting provided by some 3rd party. Call me paranoid but the fact that my source code is running on a third-party server, which someone has the privileges to access anything/anywhere on the server, makes me feel uneasy.