Hellfox,
We at Team Ulysses have been through the ringer with someone who claimed our code as their own.
The worst part of it was that we pretty much only ask for a credit where appropriate, in a readme and or credits file, not within the code file itself.
The author was quite offended that we asked for this aloud.
Lua is indeed intended in an open source environment.
I'd recommend a Creative commons license also, and simply remember that some mean people exist and won't respect it.
Those who are worthy coders will, and may assist you in learning if they have deriviative works of your original code that add new and exciting things.
The UTime project here is a good example of that....several derivatives for the various years of SQL modules that have come out over time have helped keep improving it and keeping it alive.