Hey, glad I can buy old games for some bucks, but when will we buy games with other languages than the english one ? It's not a real problem, but it's more comfortable to play in our native language.
Thanks for your answer(s) :)

Other languages will probably be offered once GOG leaves beta. As to when that will be, no one actually knows.

A number of games come with other languages built in: Here's a list
Only English is officially supported by GOG (for now), but the community here can also help out a fair bit.

I guess it depends (at least partly) on wether GOG got the rights to distribute each game in other languages than English.
I doubt the list is complete, so if you know of a game that's not listed but where the GOG version does contain other languages, please post about it in the thread and I'll update the list (I can only add games I've bought myself if I even realise the option is there, and that other people tell me about).

if you are a modder, you could find the games language files and translate them.
also, you can help by promoting the site, the more people that now about it, for sure the shorter the beta will be.