GPL is not 100% free, but it has it's uses: it is what moves the Linux comunity. It prevents what happened to some previous unix works that some comercial version took over and the comunity disbadled. But Lua is a libary, so it is to be used as a *part* of a system. I think that this is the big difference: not all system will have the same licene, so no limitation is better. There "could" be a comercial version of Lua, 1000% better, sold for US1000,00,ドル but who cares...I don't think so. I don't class the GPL as free because it's not free of restrictions. It has several, and for some show stopping, restrictions.
Alain