The source code of VVVVVV is now public! https://github.com/TerryCavanagh/vvvvvv
I really TRULY don't understand why people care about this. Updating is not that hard, and usually automatic. The only possible group you'd be servicing would be the people who pirated older versions of VVVVVV, so they'd be forced to buy it. And that's GOOD! That'd make you more money! And even if they were creators, they can just get the updated M&P. Trying to keep compatibility with old, obsolete versions doesn't make any sense.