It's a fork of App Inventor[1] so it's essentially a new version, built by people that built the original version[2].

Honestly it would not have been disingenuous to exclude that tiny link clause altogether, but now they're being punished for transparency, because people are too lazy to click on the the "About" link for the page they provided.

[1] http://techcrunch.com/2016/03/05/mit-spin-out-thunkable-hope... [2] http://appinventor.mit.edu/explore/our-team.html