r-ichi-e: Óne word of clarification: you can transfer (and install wherever you want) your downloaded install packages.
Transfering already installed games could be sometimes troublesome if not impossible (but why would you do that when you have unlimited access to your installers anyway)
metrallagame: You made me confused again wdym by that? Why is it impossible to play a game in a different pc if u already have downloaded it? i dont get it
If you install a game on computer A and play it for a while, it is difficult to transfer that same installation to computer B. You can always, however, install it fresh on Computer B. This isn't really a GOG problem, same holds true for most software installations.