Web app for browsing, reading and downloading eBooks stored in Calibre
...Restrict eBook download to logged-in users. Support for public user registration. Send eBooks to Kindle devices with the click of a button. Support for reading eBooks directly in the browser (.txt, .epub, .pdf, .cbr, .cbt, .cbz, .djvu).
...Importantly, it has an incredibly permissive Free BSD license. The EPUB standard is a widely used and easily convertible format. Many books are currently in this format, and it is convertible to many other formats (such as PDF, Mobi and iBooks).