It is, as a matter of fact. When Fry recorded his voice for those audiobooks, they were copyrighted. Reproducing the contents of those works as they have is, arguably a violation of copyright.

And when you compare Steven Frye to Pepsi Max, that’s a false equivalence, because you’re comparing a copyrighted material to a trademarked brand which are two different things.

Still, to your point of theft, nobody is taking anything from anyone. They are using something without permission, and that still falls squarely as copyright infringement, not theft.