[2020] Is the music in C:S copywritten?

Depends on the radio station. If you open Options and go to Audio, you can see which radio stations are copyrighted and not available for streaming/videos.

Originally posted by me22ca: All of the music is subject to copyright: https://www.copyright.gov/help/faq/faq-general.html#mywork

So it depends what you mean by "your own video".

- If you're streaming CSL itself, and the music is playing as part of the game, the UI in the game has implied to me that they consider that fine for everything but Gold FM.

- If you're making some other video and use the CSL music, they'd be completely justified in DMCA takedown-ing it. It's probably not licensed for that.

If you're doing the latter, then perhaps start from https://creativecommons.org/about/program-areas/arts-culture/arts-culture-resources/legalmusicforvideos/ or otherwise search for royalty-free music.

This is correct. As long as we're talking a stream/video of the gameplay, you can have the music from the game, with the exception of any listed in Options, Audio (I think it's just Gold FM, but I don't have any of the paid radio stations, so always check just to be sure). :)