With the obligatory "I am not a lawyer" disclaimer:
Akien {l Wrote}:- Am I allowed to do so (let's say according to US copyright laws)?
There is no law that forbids placing a license on your work in any circumstance. A license is permission you grant to others. I am really annoyed that some people believe, for no legitimate reason, that they aren't "allowed" to give people permission to redistribute
their work just because it has some sort of relation to a proprietary work.
Of course, fair use is U.S.-specific. So for example, if you make a gameplay video of a proprietary game in the U.S., while of course you can put CC BY-SA on your work, it may still be illegal for people in other countries to distribute it, depending on whether their countries' "fair use" or "fair dealing" laws consider your use to be fair.
Akien {l Wrote}:- If I am, what does it mean for the video's contents? If someone takes a screenshot of the video, it's still CC BY-SA. So then we have a CC BY-SA screenshot of a nonfree game, and we'll get another troll like we had last year to extract all the sprites they can from the screenshot and distribute them under CC BY-SA too as libre assets.
Your work is the video, not the components of SuperTux within the video. So, for example, if you were to choose CC0 as your video's license, it would not be legal for someone to isolate the Tux sprites and distribute them under CC0, because those pieces are copyrighted by someone else and copylefted.
Akien {l Wrote}:Or is there a fault in my reasoning? We had a lengthy discussion about this stuff for a Godot video trailer (
https://github.com/godotengine/godot/is ... -197811117), but as we're all clueless in the end we're likely going to use CC BY-ND + get approval from each game developer/publisher for using gameplay footages of their games so that we can't do anything wrong.
You can't get into trouble by choosing a libre license for
your work. If someone tries to use your license as an excuse to extract works contained within that were copyrighted but fair use, that's their legal problem; the copyright holder of the work you are making fair use of would have to sue that person, not you. It would also be exactly the same if your license was proprietary, because your work isn't even involved at that point.
You don't need to use YouTube's license field. Just mentioning the license in the description is sufficient. Though really, the best thing to do is to mention the license directly in the video.
EDIT: This might be useful for someone, so here is the statement related to fair use I made for a fangame I made recently:
README.txt of Kitten Command {l Wrote}:COPYRIGHT AND FAIR USE NOTICE
This game makes use of certain copyrighted works without the permission
of their copyright holders. These are small components of Super Mario
Bros 3, Super Mario Bros, the Japanese Super Mario Bros 2, and the NES
port of Contra; as well as the Mario Techno Remix by Paul Soh. More
details about these works can be found in data/LICENSES.
United States copyright law includes the doctrine of "fair use", which
allows use of copyrighted works without permission of the copyright
holders. See 17 U.S.C. § 107 for details. Unfortunately, fangames have
not been specifically tested in court, but it is my firm belief that my
use of these copyrighted works is fair use, based on the following
points:
1. Kitten Command is distributed entirely non-commercially. To be
perfectly clear, this is not a primary foundation for my claim of
fair use. I believe the use would still be fair use if it was
commercial. Nonetheless, the fact that the use is non-commercial is
worth mentioning.
2. The purpose of Kitten Command, as a whole, is entirely different from
the purposes of the copyrighted works being used. Put another way,
the use is transformative. As a result, the use does not diminish the
potential market for or value of any of the copyrighted works used in
any way. Kitten Command is not a replacement for any of these works.
3. Only the portions of the copyrighted works needed for Kitten Command
are included in this distribution. The total amount of Super Mario
Bros 3, Super Mario Bros, the Japanese Super Mario Bros 2, and the
NES port of Contra used is small compared to the whole of the
respective works.
4. The copyrighted works used are only small portions of Kitten Command
as a whole.
Anyone wishing to redistribute Kitten Command has my permission to do
so; you will find that all of my work is released under libre licenses.
However, if you live outside of the United States, please check up on
the laws of your country regarding things like fair use and/or fair
dealing, as different jurisdictions have different rules regarding this.