It's French or Spanish for free, because in our languages we split the concept of free beer and free speech into two words.

Gratuituous could be used for free of charge since it's what we used in latin languages (which I suppose is the same root as gracious - at least in formal french we replace gratuit with gracieux to mean the same thing).

So I wonder if English, tired of borrowing a strange word, will use gracious or gratuitous some day to denote free of charge ! That would maybe avoid all these questions of what libre means !