Looking for alternative Collaborative Developing Environments

I'm interested in Collaborative Developing and I was wondering if there are alternative solutions than using UNA (example video) from N-Brain. Free would be even better, but I guess that's not an option which such technology.

PS: The main future I'm looking for is working real-time with multiple persons in the same code.

Solution

If you're in Mac world, SubEthaEdit is a good option. Not free, but €29 isn't bad.

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