SourceSafe also allowed you to checkout files in non-exclusive mode which made it more like CVS. It also had a way to share files across different directories, a feature we emulated in CVS by symlinking files in the CVS_ROOT.

Also, fun fact: SourceSafe was the first cross platform VCS I used. There were Mac, Unix, and dos/windows versions. Then Microsoft bought it and axed everything except dos/windows. :-(