First, thank you all for your comments and suggestions.

1. You are right about the license. It’s (unintentionally) misleading. I’ll change it soon to pure MIT license.

2. @okal, @Turing_Machine: yes, ePub will be supported and more formats will follow.

3. @gnufs: it uses PrinceXML for PDF publishing because it’s, by far, the best library I’ve found for HTML to PDF conversion. Do you know any other free/open-source library with the same or superior features?

4. @mrleinad: yes, I’d love to use a shorter and cleaner URL; but it’s really tough to find a good and unregistered domain with the word “book”.