This means that the solution you opened is under version control, like Team Foundation Server (TFS). To work with the versioning features you need a special version of visual studio.
As it seems (assumption based on the error message) you can use the source from the project, you can build and start the programm, but you cannot commit any changes you made to the versioning repository.
The wikipedia page about TFS explains pretty well what TFS is about: http://en.wikipedia.org/wiki/Team_Foundation_Server
If you working with the code for yourself, it shouldn't be a problem. If you work on a team project, using TFS as versioning system, you would have to upgrade to another VS version.
Maybe this stack overflow thread can help you a bit: Connect Visual Studio 2010 Professional to TFS