Can you give one or two examples of this?
You have to wonder when an artist finds it easier to copy the albums from such sources than from the collection of their own.
I can't find the article I read this from, but a few years ago (back when GoG was 'Good Old Games'), there was an article about how license holders often didn't have any of the actual game material, they just happened to own the license to them through mergers / aquisitions / bankruptcies / whatever. So GoG would have to track down old published copies of games for them (either through second hand shops, or eBay, or the internet) and then restore them (using a combination of internet / open source tools, or their own work), in order to sell them on their store.
Presumably, if the internet 'pirates' had not done the work of backing this software up and preserving it, a number of GoG's titles simply would not exist today in any form, and could no longer be sold (even if the license holders wanted to)
I would imagine downloading a 'pirated' copy of the work is not piracy when you already hold a valid legal license to that work, by definition.
You are not necessarily in the clear; it depends on type of license you have, and whatever personal copy/fair use protections your country has.
https://www.gog.com/forum/general_archive/gog_arcanum_releas...