Question about rules regarding using assets from other games in mods

[Mernom]

Is it allowed? I bought a copy of Incoming Forces+Incoming, and all of their sound assets are in plain wav format (ogg for the music).

[Honktown]

It'd always be polite to ask. There's usually two cases: 1) profiting. Fair Use is a specific concept, of using something copywritten and used in a limited way, normally not in a way relevant to the original thing (don't make their game, don't claim its yours, etc). 2) misrepresentation. If a group doesn't feel that you should be doing <thing>, they can ask you to stop and you have to obey or face legal issues (cease-and-desist or worse).

Hardcorio uses a bunch of Starcraft 1 stuff, but Blizzard probably doesn't know, and even if they do, it's not like the mod is an rts mod or misrepresents Starcraft. If the author got a letter though he'd have to replace the assets.

[DaveMcW]

No, you must have permission from the author for any assets you use. The easiest way is to find assets that are licensed under a Creative Commons license.

[Mernom]

hmm. How about a mod that can make use of such assets, if the user owns them and packages them, but doesn't actually redistribute them?

[BlueTemplar]

Yes, this is the usual way in which mod authors work around these issues :
https://lubiki.keeperklan.com/html/dk_keeperfx_read.php

Remember that KeeperFX needs the original CD. The files installed
on disk by original DK setup are not enough. Also, you must select
the "keeper" folder from the CD content list. Selecting root folder
of your CD, or selecting installation folder on disk, won't be enough.
For the GOG version select the 'Dungeon Keeper Gold' folder the game is
installed. For EA Origin select the 'data' sub-folder to install.

[eradicator]

hmm. How about a mod that can make use of such assets, if the user owns them and packages them, but doesn't actually redistribute them?

That won't work well with the mod portal. Unlike in other games factorio mods do not come with an "installer" and requiring users to do manual work is going to severely limit the group of people that will even try to use your mod.

Also Incoming, lulz. Sure got some old stuff there :D. According to wiki neither the Development Studio nor the Publisher exist anymore, so who knows who has the rights now (if anyone at all).

[DaveMcW]

who knows who has the rights now (if anyone at all).

Well, someone is selling it on Steam. https://store.steampowered.com/app/283390/