Nice! Better than Nicalis' one. Too bad that the two player mode was made by them.
I noticed that the level editor is not working. It opens, the game either hangs or just stops receiving inputs (can't tell). Oh, it uses mouse and a lot of key bindings on Windows. That's why, probably. Maybe just disable it?
I think custom levels loading is not working either?..
For a second I was really excited about this, but if you go to the repository on GitHub and check the license you'll see how the headline is misleading: the game is not "open source". The license imposes restrictions on redistribution, stating that you cannot sell the original or altered code in binary or text form, which goes against the definition of open source.
That said, it's nice that the source code was made public, even if it is pretty messy.