Well, the INT is not about authority, it's about cooperation on an equal level. Roget is there to represent EN, and given the fact that other branches have four representatives, he's a bit alone there, but that's a matter of Internet Outreach I guess. Anyway our doors are open to anyone.

I think anything from a shared policy to a simple guide explaining the license for some examples that usually come up would be welcome, I'll bring that up among INT's staff though.

As far as I know we've yet to be informed of any German-language license violations, so that's not a matter of concern. Most foreign language license issues are Russian and Japanese, and both of those branches have (or at least have had in the past) staff to handle them, if not a "team".

I'm happy to work on clear licensing guidelines, but that'll probably be a project for all the branches to vote on. I'm not even a member of -INT, so I have no authority over the other branches, unless they all decide to give me that authority (which I'd say wouldn't be a great idea). Please ask your Branch's admin staff and the rest of -INT if cooperating on a group licensing policy is something that would interest them.

so, according to 2), YT-videos may be any license? I'm not familar with US law.

We, the German branch, do not seek to prosecute license violation, unless someone wants an official cooperation or tries to mess with us or our authors. EN is the license holder of the SCP-license in general, and we are not required by law to defend our license to retain the right to do so. And as you we don't have enough time to cover everything we should or might want to.
In fact I'm asking because I know that this question has arisen among the YouTubers. I'd like some clarification for us as well as for them, to prevent possible arguments in the future, and to even the path for more cooperation with them.

A clear and simple guideline regarding the license, its use and legal background including international law would be nice though.

1) CC-BY and CC-BY-SA are compatible.

2) It is the current opinion of myself as Captain, as well as that of my predecessors, that audio readings of the work are sufficiently transformative with the material so that it counts as Fair Use under United States law (which is the jurisdiction we use as a matter of convenience).

3) While this has never been explicit policy per se, the guiding light of Licensing Team since before my time is that we try not to pester innocent fans, a school of thought that's been affirmed by multiple -EN admins. We're a group of a handful (currently just two[!]) overworked volunteers, we don't have the time or the will to go after anything but serious products.

3b) Additionally, it's been deemed best that we leave the minor stuff alone. Think of it like how media companies ignore freelance artists using licensed characters at fan conventions. We could (if it was ruled not to be Fair Use) come down on it, but it'll win us nothing and piss off the people who are helping our sites grow. Just a bad move.

4) In response to your Germany-specific question, the only reports I can find refer exclusively to CC-BY-NC, a license distinct from and incompatible with CC-BY-SA. This incompatibility was, for example, the crux of the recent issue with the -RU branch. If I am wrong and this decision refers to more than just the Non-Commercial License, please correct me and I can give a more in-depth explanation.

5) A general statement about the -EN Licensing Team. We do not presume to speak for every branch. We merely handled the Russian Branch matter because it needed to be handled and we had the staff to handle it (plus our hands were forced in a very public manner). With the exception of "all branches must use CC-BY-SA", which is a legal truism at this point, very little I say must be taken as gospel by staff at the other branches. Other branches are free to develop their own licensing standards for dealing with material so long as those standards do not violate CC-BY-SA 3.0. The -EN branch licensing team is always happy to offer advice and answer questions, but we do not inherently possess any authority over other branch's teams. In fact, for reasons of time and and language barrier, since at least my predecessor's tenure, we have left material in the language of a translation branch for them to handle. We've largely failed at communicating this, however, for which I personally apologize.

5b) If there is interest, I would be happy to participate with other branches on equal footing in setting a formally decided procedure for all branches to deal with licensing matters. I, however, have neither the ability nor the will to set them unilaterally.

I'm the Ambassador of the German branch and I would like to ask what license YouTube videos with SCP-content have to be under and why.

Especially readings of SCPs and SCP tales. According to my information, readings are to be published under the YouTube-CC license. Though there are some problems with it and some questions.

First of all, the YT-CC-License is CC BY 3.0, which, as far as I understand the CC compatibility info, is not compatible with CC BY-SA 3.0. In the RU-Incident you said the license of SCP-content can not be changed under any circumstances. Wouldn't that mean that there either may not be SCP-content on YT at all, as it doesn't provide a compatible license, OR that it can be published under any license, as the license info can be specified in the description?

Second, such a video contains other things, like music, an actual video, a title, the readers voice etc. so it is a mixed work and not all parts are necessarily SCP-related. The SCP is only a part of it. And we can publish SCPs under CC BY-SA 3.0 containing work (e.g. images) under another license. So the question some YouTubers may ask is, why can't they do the same?

The actual problem some YouTubers have with this license is theft. Some are constantly filing take-down-requests because some users steal the title, some steal samples, some release the whole video under their flag etc.
Some are using images or music they have bought, that are part of the video though under another license or copyrighted. Putting the whole video under a CC license would violate those copyrights, wouldn't it?

tl;dr: Do SCP-readings on YouTube have to be under the YT-CC-license and why, or may they be released under any license and be attributed accordingly?

Also could you please explain in a few words why and how the CC license is applicable outside the US, for those who deem it invalid e.g. in Germany?