An idea I just had regarding ebooks and the library system led me here...

Say a library wanted to set up a proprietary program and ebook format to offer ebooks from their website that could be downloaded, but would 'expire' in a set period—say 30 days. This way they could offer the same selection for download as they did at the physical location, but on the same principle. Would C or C++ be the preferred method of designing said program, or would another method be better? At the simplest level, what would be involved in something like this?

Just a thought I had, while I was wishing I could just download any book I wanted to read—legally.