Real-time collaborative edits in IDE is probably not desirable because that would make code uncompilable unless all participants are done at the same time. This means you can't frequently run and test your changes and see your test getting passed. Your edits would block another person and vice versa. A good alternative is continuous integration where you can push code at every time your tests passes and immediately do pull afterwards to get other people's changes. This can be done by simple scripting with most version control systems.
One of the app I frequently use for collaborative code discussion is http://collabedit.com.
