in reply to On providing documentation with your modules
I think you definitely shouldn't copy and paste, because duplicating documentation, like duplicating code, can lead to a maintenance nightmare. You'd need to keep abreast of changes, and keep things updated, and I'm sure you don't want to do that.
I'd suggest that you make it clear in your own POD that extensive documentation is available elsewhere, and where it can be found. Provide links to this other documentation, so that those viewing the documentation in a format where these links are useful (like on the CPAN web site) can easily get to the other documentation without rummaging.