NQC is
free software, released under the
MPL.
It can be used as an alternative to the crappy
GUI that Lego ship with
Mindstorms. Kids (an I mean little
kids here) will enjoy the simple GUI development environment. People who are already
programmers will find it infuriating, and will much prefer the power and flexibility of NQC.
The author of the languge, Dave Baum, also wrote the book, Dave Baum's Definitive Guide to LEGO Mindstorms, which is rather good.
The NQC homepage can be found at
http://www.enteract.com/~dbaum/nqc/index.html