My mods and their source assets are available under relatively informal terms. I generally reserve the right to change anything at any time, but you can consider my creations as "Open Source"-ish with the requirement to share changes under similar terms. The terms aren't entirely compliant to the Open Source Definition, though, as the UT EULA still imposes some restrictions and I also exclude certain groups and "fields of endeavor" from using my work.
You will likely find the following text prefixed to most of my newer UnrealScript source files. (Should it be missing, please treat the file as if it was there.)
With these three statements I tried to sum up my intentions for source code reuse in as few text as possible. This page (its canonical URL is http://wormbo.de/license/) exists to explain my intentions in more detail and to clear up potential misconceptions.
These statements always apply in conjunction with the Unreal Tournament game's End-User License Agreement (The Unreal Wiki provides non-authoritative copies of those EULAs for UT2004 and UT3.), particularly the section about "Editor and End‑User Mods". (Note that the UT EULA applies to the game, the editor and also all third-party mods, but not necessarily to the source assets for such mods, unless derived from UT content.)
I usually do test my stuff, but I can't rule out all potential errors. While I don't expect my mods to fail in such spectacular ways that they cause any kind of actual damage on stuff you own or anything to that extent, I cannot and will not take responsibility in the case it actually happens. If you downloaded any mod, not just mine, you implicitly accept the possibility of that happening. (If you don't, you might as well leave the internet right now and never look back.)
In particular, if anything "bad" happened to you or your property and you intend to sue me or anything like that, don't. You will be wasting the time of everyone involved, including yourself. This is especially true if you constructed something important using the sources or binaries I provided and your damage resulted of that breaking down. I explicitly warned you, so you can only blame yourself under those circumstances.
I live in Germany and release my mods from here. So if you plan on taking me to court anyway, do so here. I know some US courts think they can rule over the entire world, but seriously: If I get a letter summoning me to some foreign court, expect my response to be a laugh, some eye rolling, and optionally a post on Twitter making fun of you. Don't like to travel internationally to sue me? How about simply contacting me first? (Ideally without attacking me right away, because that may result in the same type of response from me as described above.)
Apart from occasional donations, I don't make money from my mods. They are truly "freeware". I don't even have advertisements on my website. (If you see any ads anyway, you might want to check your computer for infections.) Releasing mods is my way to give back to the community. As a result, I don't like seeing others making money off my work without my permission.
If you plan on selling anything that makes use of my mods (beyond providing game servers with my mods pre-installed – I'm okay with that), please contact me first, offer me something in exchange (ideally something more tangible than "fame and honor") and I'm sure we can reach some kind of agreement. (I have to admit that never happened so far, and I don't really expect it to happen any time soon.)
I hope I don't need to mention that using anything I release in safety-critical contexts (medical devices, nuclear power plants, car/aircraft control, etc.) is not only dumb and dangerous, but also likely some kind of commercial use.
I realize there are uses that are seemingly non-commercial that I still wouldn't want to be involved in. Obviously I don't want my stuff to be used for criminal goals. But I also don't want certain organizations, like the military or any (pseudo-)religious cults, to use it.
"But you didn't mention the military!" – True. However, I have yet to hear about wars where nobody's human rights were infringed in any way. In other words, it's sort-of covered.
"But in your mods there's war and cruelty!" – Seriously? It's a game! Nobody really gets hurt (except maybe their pride as gamers), regardless how cruel the content seems. Yes, I'm a member of the UT Jailbreak team and yes that mod has some seriously morbid "execution sequences", but it all happens in the game only. If you can't distinguish that, you should probably not be playing something like the Unreal Tournament series in the first place.
That restriction extends to free games like "America's Army", intended for recruitment. If you want to promote your product, organization or religion, please do so without my mods or source code. I suppose I can't prevent you from using them internally, but you should know that such use is generally included in that restriction. If your morals are worth anything, please respect my stance on this topic.
You are allowed to reuse parts of my source code and you are allowed to package the unmodified binaries I compiled with your work. Feel free to export sources from the compiled packages and dissect them in any way you like.
The only notable exception is Anti TCC. I stripped sources from the package and made various decompilers fail on it intentionally. I will not release the source code to anyone, for any reason. Anti TCC is old and the sources can rightfully be declared a big mess. Trust me, you will hardly learn anything from it. And if you're going to write an anti-cheat tool, there are certainly better ways to do it. Anti TCC grew organically far beyond its originally intended purpose, piling up design debts like big commercial products. You don't want to see the source code. Just trust me on that.
Other than that, the only thing I ask for is common sense. Never, ever, release a compiled package with the same name as anything anyone else ever released, even if it's just on your own server. Particularly, if you modify one of my maps or mods, please change the file name of any package you modified.
I expect you to release the parts of my source code you used under similar terms as I did. You don't have to apply these terms to your entire mod, but you also can't just release it under the GPL (which – by the way is – incompatible to the UT EULA), some Creative Commons variant or into the public domain – my terms are both more strict and more loose than the GPL or CC-whatever and definitely more strict than CC0 or public domain.
That's not an absolute requirement, but it's really common courtesy and you'd make this little wormy coder happy. Also, the community is very aware that certain individuals are stealing others' works and release them as their own. If you don't mention where you got something from, people may accuse you of stealing, even though you did nothing really wrong. Just mention me somewhere in the readme or even just the source code.
When you mention me, be a bit careful about the wording. Even when I encourage you to extract, read and modify the source code of my mods, that does not mean I endorse your results in any way. Don't get me wrong, I just don't want people come yelling at me that I supposedly said something was good while they think it's utter garbage.