Any contribution to the project are seen as copyright assigned to Hampton Catlin, a human on the planet earth. Your contribution warrants that you have the right to assign copyright on your work. The intention here is to ensure that the project remains totally free (liberal, like).
That's a curious setup. The license is MIT so you're not getting the "if you distribute it you have to use the same license" that you get with GPL. So as long as the contributions use the same MIT license why does the author need copyright assignment? The MIT license is simple and standard enough that relicensing doesn't seem like a likely need.