Legal issues when forking Lua?

Question

I've been developing a highly modified version of Lua (including a rewrite of the sources to keep a better maintainability). Right now i'm at a point where I would consider forking Lua, and possibly re-release it under a different name (so people don't mistake it as the original Lua interpreter).

Of course the resulting Interpreter and compiler will be Opensource (MIT License, just as Lua5.0). but I wonder if that would be just fine with the Lua license? Can I use the Lua sources to continue my own work? do I have to keep the copyright notes?

Answer 1

My first suggestion would be to send an email to the Lua folks. I'm 99,9% sure you won't have any problem.

Now that I think about it, another guy create a language called "Idle" which, if I remember well, is heavily based on Lua.

As long as you properly show the due credits and fairly represent the differences with Lua, I'm sure you'll be fine.

Answer 2

The 'polite' thing to do is to use a different name and clearly credit on your documentation; stating that it's based on Lua but not 'official' Lua. AFAIK, the licence doesn't legally require even that; but it's what you're expected to do.

Remo.D mentioned the Idle case; personally, i don't like the attitude of "this fixes the problems with Lua" that i kinda read on Idle's webpage and his messages to the Lua list; but it's widely recognized that he's doing the right thing: a different name and openly showing credits.

If you want to be really popular in the Lua community; you could try to release your code not as a fork of Lua; but as a set of patches to the core. It's more work, I'm sure; but it has a much higher chance of being used by more people; and maybe (big maybe) some ideas could eventually be integrated in the core.