Puffbringer: For anyone who doesnt want to go through this whole song and dance to install Seamless HD mod, someone already compiled everything you need to install it on GOG version of the game. All you have to do is literally copy/paste the contents of the zip file into the game's directory, and it works without any issues. I don't believe it includes HQ Audio pack, but you can install that separately if you wish.
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VaporwavePinhead: Pretty sure those are borderline piracy: these "patches" pretty much redistribute the vast majority of the games' content, and embed other people's work without even asking, putting them too in legal danger.
These are not just patches, these are full mods that feature completely new 2D elements for each game. The necessary mods to run this are included for convenience sake because it's too much of a hassle to install everything manually. It's just too much for the average user, as seen in this forum. Every included mod is credited and linked to.
In regards to included files owned by Capcom: Many many mods include files which belong to the original publisher - even the RE4 HD Project. You still need a full copy of each game to run the mods and every user that has asked for the full the games, is being redirected to GOG. In the end GOG and Capcom are profiting
from these mods that continue to improve upon their creations.