Let's go easy on the proselytizing, everyone.
Spoon, the bottom line is that we heavily encourage everyone who doesn't have a legal copy of the game to purchase one from GoG, but we obviously can't force anyone to do so. The reason that the full game was available for download from this site for a period of time was because, at the time, there was literally no way in the world to legally purchase it outside of the odd ridiculously marked-up eBay or Amazon copy. The Powers That Be here decided that preventing the game from vanishing into obscurity was worth the technical copyright infringement. Then along came Good Old Games, which offered the original retail game for a very cheap price and with no DRM strings attached. Not only do we want people to support the original publishers of the game now that it's been made available again, but we'd also like to support GoG as a way of thanking them for the excellent product they're providing. But like I said, it's all up to you in the end.