You can create a vitual environment (a virtual machine) with limited internet connection (only to specific servers - git/svn server, database server, etc) and no copy/paste possibilities.
This virtual machine would be a standard environment with common developer tools.
At the office a developer would remotely connect to the virtual machine and start developing without being able to steal the code.
Of course he could print the screen or type the code on another computer but it's still very hard to steal.
