So where is the source? Also I am fuzzy on whether or not this is a license violation:
[TeX] This program is copyright (C) 1982 by D. E. Knuth; all rights are reserved. Copying of this file is authorized only if (1) you are D. E. Knuth, or if (2) you make absolutely no changes to your copy. (The WEB system provides for alterations via an auxiliary file; the master file should stay intact.) See Appendix H of the WEB manual for hints on how to install this program. And see Appendix A of the TRIP manual for details about how to validate it. TeX is a trademark of the American Mathematical Society.
I know they are altering the translation not the WEB source but that is still the Tex program.
I don't think there is a limitation on selling TeX derivatives. A lot of commercial products based on TeX have been created, such as Scientific WorkPlace. I would be concerned about cweb, the translation of TeX from pascal to C used on unix.