IMHO the GNU FSDG and typical copyleft licenses require build scripts because building certain programs involves elaborate procedures, and depriving users of Makefiles, configuration programs and whatnot would be a relatively trivial (and thus prone to abuse) way to keep users from being able to enjoy the freedoms to adapt and to improve the program. licenses and guidelines that strive to defend users' freedoms thus must stand in the way of such trivial attacks, just as they they do of more elaborate attacks.