The Homeworld 2 modding community has had a checkered past on the subject of intellectual property. Heated words have been exchanged on more than a few occasions where the author of one mod used content from another without the explicit permission of the latter mod's author.
In March 2015 a Gearbox forum thread was opened to discuss who is in the wrong and how future mods should proceed. Below, I have paraphrased what I believe are the most important parts, but I strongly suggest all mod authors read the original thread
It is not currently (nor is it likely to be) Gearbox's policy to police mod content. They made a product, reserved their rights to it, and put it up for sale. However, content host like ModDB and Steam are bound to abide by the policies and demands of the DMCA and Safe Harbor Provisions. Thus, mod developers should plan to abide by the policies and terms of service of their distribution partner. It's really easy to file a DMCA, and if somebody says "that's mine and I don't want it where it is," ModDB and other hosting sites have to respect the Cease&Decist;/DMCA requests or they'll be taken down.
- BitVenom, Gearbox employee
Mod developers sometimes don't understand that scripts they create in LUA for Homeworld (as an example) aren't the property of the game's developer. It is your content and as intellectual property, you'll always be considered the author. That being said, you can't sell it because you're not the owner of the game upon which you are making modifications. When a game supports modding (such as Homeworld), mod developers have to respect the copyrighted content. You're not allowed to do whatever you want, and and you're typically not allowed to make profit of your content.
There's a slight difference between original content and stuff inspired from commercial IPs like Battlestar Galactica (as an example). If you model/texture the Battlestar Galactica, the model and texture belong to you, but you don't own the universe and the original idea behind it. In that sense, mod developers have two ways to make sure their project won't be hit with a C&D and their content removed from the host site:
- Contact the original owner of the copyrighted franchise and ask permission. Frequently you will be granted permission unless what you propose would be in direct competition with a product the IP holder has or is producing.
- Don't contact the owners and take the risk of receiving a C&D later, and all of your work will have been for nothing.
You shouldn't use, in any way, content from other mods, games, and/or creators that are not yours without permission. If you don't have the permission, you risk your content being removed from the hosting sites.
- Erayser, Thibault Testart, ModDB editor and mod developer
Things like Public Domain, Creative Commons, and General Public License exist to allow authors to say "Hey, use my stuff!" and still retain some rights. We encourage those interested in sharing to spend five minutes to generate a license. Years down the road, somebody may want to use your content, but they may not be able to contact you.
Keep in mind HOD files for Homeworld Remastered cannot be extracted, which was not the case in Homeworld 2. If you want people to be able to use your stuff, post the source materials that go into generating a HOD file.
- BitVenom, Gearbox employee