OldFatGuy: You're very welcome. I can provide a link for free Arena and Daggerfall for your friend (at least I used to be able to... it was right on the Bethesda website) if you would like.
SirLeedle: I’m aware of the promo Bethesda did for TES’s anniversary (read about it on Wikipedia), where they gave people Arena and Daggerfall for free to celebrate TES’s birthday, but you can’t navigate to the link from Bethesda’s site anymore (you can, however, by google searching). My friend is very likely to buy the original Quake within a week or so of registering on GOG, so he probably won’t get around to downloading the games from Bethesda’s site before he receives them on GOG, so the link won’t be necessary. Thanks for offering, though—it’s a kind gesture, and it speaks volumes about the community on this site.
Just to reiterate, DON'T get the games from Bethesda's site (unless you want "original" copies for archival purposes or something). There is literally no benefit that I'm aware of to using those, versus the GOG versions or the community versions linked to from those UESP pages. Even if you have the GOG versions, I'd still recommend checking out the ones from Wiwiland. (As with pretty much all later BethSoft games, bugs abound, and the fan-made patches and other fixes and utilites help a bit, especially for
Daggerfall.)