False. First of all, GLua is different than Lua - there are many custom function which documentation is available in - how not - GMOD WIKI!
Also, lets go search for a Hebrew tutorial, shall we?
Don't be an ass. "Oh let's find one of the least widely used languages and go and demand tutorials."
Hebrew - Israel / Palestine
English - 50 countries and multiple territories.
Spanish - 21 countries.
Russian - At least 14 countries.
Arabic - Most of the Middle East and North Africa.
Considering that most of the GMod playerbase is in Europe or North America, I'm going to go ahead and assume it's safe to say that most of the playerbase can speak somewhat decent English or at the very least read bits of it. Again, teaching Lua (GLua) in other languages is a pure waste as it's English.