I'm not sure I'd say yes. I'd say "it depends". I know YouTube itself offers music tracks that may be used. I'm not sure if it's possible to have an existing video on YouTube, then upload and add a music track. But that's what this question sounds like.
As I understand it, while the media supplied with Camtasia may be freely used in a video created with Camtasia, you are not allowed to use it separately for something that was not created using Camtasia.
Again, TechSmith has final say on anything like that. But I believe I've seen them reply to questions like this with essentially what I said.