The copyright Office's FAQ on derivative works is at:

http://www.copyright.gov/circs/circ14.html

Basically, if you make non-cosmetic modifications to the code (even then, things like PK ranges and cabals were in), all of those modifications automatically fall under your copyright and cannot be used by others. That version belongs to you.

ROM/Merc/DIKU's creators retain the copyright on their respective works, and our work (of course) is no hindrance to whatever they choose to do with it. They cannot, however, publish our version of the code without our consent, because that would violate our copyright on that version.

valguarnera@carrionfields.com