"Develop web applications," "pick a language"... that's programmer talk. You want source control, not a web app: look into git or Subversion.
There's a learning curve if you've never used an SCM, but it's a rite of passage for any web dev, just like the moment when you realize someone overwrote 2000+ lines of your code that you just startingstarted overwriting as well, and the drunk googling for how-to's that usually happens a couple hours after that. Bad scene, easy to avoid.
If you need a web interface, try here for hosting, host your own gitweb (various PHP, Ruby, and Perl apps), or just use a GUI client. I just keep my private/commercial git repositories spread out on dev servers and a couple laptops, easy & cheap as long as you have permissions to install it somewhere.