We announced GitHub integration for TFS several weeks ago and there are various integration points with SVN, for example, out there.
So why use TFS? A common misconception is that TFS is a version control system and that it only works for Windows developers - .NET developers. Not true.
Think as TFS as a collaboration tool, so whether you're a Product Owner, a stakeholder, a project manager, user experience, business analyst, architect, developer, tester, builder, operations or end-user. TFS enables the collaboration between these roles through work items. As a result of this collaboration a rich reporting experience is provided, either in VS, Office or SQL Server Reporting Services, for example. We have customers that use only specific parts of TFS.
Onto non-Windows developers. If you are a Java developer on LINUX, you have Eclipse, you can work with the TFS plug-in, or if you are an Apple developer, you can work collaboratively on TFS.
The number of client types is very extensive including the good old browser.
Furthermore extensibility via SDKs is available to Windows and non-Windows developers.
In Visual Studio 2012, we have some awesome developer features that enable developers to Suspend/Resume workspaces. There are Code Review features. There is a collaboration aspect where a Tester can define tests and when these tests fails, diagnostics such as Video, Event Logs, IntelliTrace, test steps can be captured and shared with a developer. All of this without having to use version control.
If you want to define software requirements and articulate and collaborate those storyboards with the development team, TFS is a perfect candidate.
So, whilst this post is not a technical one, the emphasis, is version control is a specific aspect of TFS, but there's a whole lot more to it that you can use, with having to use the TFS version control system. A lot more...