Hi guys,

I was thinking of doing a project similar to Handmade Quake - take an old game, write code to read and render the old games assets, and replicate the behaviour of the game.

I'm wondering about the legality of this sort of thing? Obviously I couldn't distribute the game assets, but if one of the requirements for the project was "first go and buy this old game on steam and install it", is that legally ok? Is it morally ok? When I've mentioned this idea to people I've had a range of responses from "I can't see how that would be a problem", to "it's totally not ok to STEAL someone else's game assets".

Any advice appreciated!
Cheers

It is fine to do that, but it can happen that owners of trademark/copyright will ask to take down whatever you are creating. That sometimes happens. So you should be ready to take everything down. Otherwise you'll get DCMA notice and youtube/HMH/whatever site you are hosting your content will forcefully do that.

Also you need to be careful to not decompile code - which is sometimes illegal depending on your local laws.

Some open-source reimplementation of games does this - asks you to take assets from Steam or your legit copy. For example, https://openxcom.org/ Also https://www.openttd.org/ OpenTTD allows you to use original assets, or the their own, completely reimplemented ones.

If running the code requires a copy of the game from Steam or GOG, and the code's entirely from scratch, then as far as copyright goes it ought to be fine.
It would be better if someone else reverse engineered the file formats in question for you and you implemented the loader entirely based off of that description, so there can be no allegation of decompiled code having made it into your version.

Trademarks may be the larger issue. You'd have to be careful how you describe the project. But depending on which game (more importantly, which publisher), it can be done without getting a takedown notice. See that list to get a sense of the success rate of such projects and to get an idea of what their legal exposure was.

The short version is that as long as you don't distribute the assets, you're not infringing on copyrights. As for trademarks, if it's descriptive use "This is an engine reimplementation of such and so by them and such" and not "This is such and so" or "This is an updated version of such and so by them and such", you're only using the trademark to say what this is in relation to that other thing, not claiming to be this thing or a continuation of it that might confuse people to think it's official.

With that said, even staying within both the letter and spirit of the law doesn't stop an IP owner from sending a nastygram. As an example: If you're trying to recreate a game by a certain Japanese company who had a bit of hit with a game starring a plumber, forget it.

(I'm not a lawyer, nor do I play one on TV, but having been in the software game for 30+ years, you pick up more than you want to know about IP laws by sheer osmosis. Still, this is just how I see it, not legal advice.)

Thanks very much for the info guys. With regards to reverse-engineering, the engine that was used for the game I am hoping to replicate, is already on GitHub, so no reverse-engineering would be necessary.

Cool, I guess I'll just do it then, but be ready to license some assets and just make a sort of clone if needs be.