That's about the size of things. The books appear to be in the public domain, so there aren't any ownership issues by definition, but we can't guarantee it in any legal sense.
Other possible legal issues (unrelated to the comics) off the top of my head would basically be patents and contractual issues. In software, a LOT of obvious, common functionality is covered under recent patent (a company called Lodsys has started chasing app developers over the idea of an "in-app upgrade button, which is absurd). And I believe that Apple has been firm on the stance that you can't offer things to the user outside of Apple's purchasing system, so it might not be something you can clear with them. But that's just speculation and a little bit of rumor.