Carradice: This sounds interesting! There are organizations that are using torrents as a way of publishing information, but one might have thought that torrents were irrepressible in nature and that it cannot be controlled who gets what once they are there. Yet if this that you mention could be done, it might be helpful for very large downloads. With GOG controlling access and versions.
Also, does not Windows 10 offer the option to download updates from peers as well?
timppu: I am not fully sure how the bittorrent protocols works with restricting access to downloads that, but:
1. Humble Bundle offers optional Bittorrent links to their downloads, so you can either download your games directly from them, or using a Bittorrent link.
I haven't tried if it is possible to use those .torrent files even when you are on a separate PC without logging into your HB account, so I am only assuming you can initiate those downloads only if you log into your HB account. I would be surprised if they are not restricted somehow, ie. if I now gave you the .torrent for my HB Amnesia game download, you could also download it using that .torrent.
2. From the past I do remember some Torrent sites where you could download a torrent only if you had an account on that torrent site and were logged into it. Meaning that even if that torrent link was on some separate torrent site (be it Piratebay or whatever), it was useless to you unless you had a valid account on that separate torrent site.
I guess I should google for this so that I am not just assuming things... either way, of course GOG could still implement optional p2p protocol into their own Galaxy client, for example. I think other companies have done that in the past, ie. I recall the Battle.net client optionally using p2p to speed up downloads, and as you said, I also recall Windows 10 might be doing that, ie. users upload stuff to each others as well, not just downloading everything from MS servers...
thats strange ,i didnt know torrent can do that , thought if you have the file structure data and trackers list you can just start downloading