It's not "potentially legal". Maybe in some dream world with pink fluffy clouds and jackrabbits happily hopping about there, but not in this real world.

It's really, really, quite simple, if you care to look at the law even for the tiniest bit. If the creators of JJ3 do not wish it to be distributed, which they have stated they DO NOT, it cannot be distributed legally. Leaked unfinished things do not become 'legal' to distribute because they were leaked before they were published and copyright was requested (if someone leaks Madonna's newest album a month before it was released, does it become legal to share her album with all your friends since it wasn't published yet?), they stay illegal since any work is automatically copyrighted by US law.

The wording of section 102 is significant mainly because it effectuated a major change in the mode of United States copyright protection. Under the last major statutory revision to U.S. copyright law, the Copyright Act of 1909, federal statutory copyright protection attached to orginal works only when those works were 1) published and 2) had a notice of copyright affixed. State copyright law goverened protection for unpublished works before the adoption of the 1976 Act, but published works, whether containing a notice of copyright or not, were goverened exclusively by federal law. If no notice of copyright was affixed to a work and and the work was, in fact, "published" in a legal sense, the 1909 Act provided no copyright protection and the work became part of the public domain. Under the 1976 Act, however, section 102 says that copyright protection extends to original works that are fixed in a tangible medium of expression. Thus, the 1976 Act broadended the scope of federal statutory copyright protection from "published" works to works that are "fixed."

United States Copyright Act of 1976

This took me five minutes of research. Please do inform yourself before making odd claims and acting on them and heaving rhetorical slurs at this site's administration.

If you want to spread your JJ3 mod, here's how to go about it:

1. E-mail its creators or a contact person of them (Dodrill?) that you've made a mod that does include the engine, and is thus not illegal to spread even with its creators' consent.
2. Ask them if they still do not wish it to be spread.
3. Rejoice, or give up.

Why do I say this? Because they have stated they do NOT wish it to be distributed, and they have actively opted to not allow it. But perhaps they can be convinced with this new situation. You need to actually try, however.