I would personally just get my hands on 2.2 or 2.3. From 2.0 onward (released in 2011) VVVVVV hasn't relied on Adobe Flash and has a level editor, for which people are still creating levels. As far as I'm aware, the Mac App Store is basically the only place on desktop where the 1.2 version is still offered.
One note though, the latest officially released version is 2.2, Terry would probably give you access to that given you bought the App Store version. 2.3 is expected to come out in a couple of weeks. The source code was (officially) made public at the start of this year though, and anyone with a little bit of know-how can create an executable of the current development version at any time.
For completeness, there's also a completely free version of 2.2 which only has the level editor and not the main game. If you're interested in a state of the art 2.3, you'd need the graphics and music assets from that version (or from a full 2.2) in order to get it working, since the assets aren't allowed to be freely distributed. But that process is pretty simple.