Abulafia has reached the end of its useful life. It is not compatible with OS X 10.9, and there are no plans at present to make it so (indeed, it is not possible to distribute a program like Abulafia in the current incarnation of the Mac App Store).
Those who are still on 10.8 or before are welcome to download Abulafia 1.5 for free, but keep in mind that the software is unsupported. The manual is also available free in EPUB (iBooks) and MOBI (Kindle) formats.
For future projects, please have a look at Burning Slug, a web-based ebook (and print book) compilation system.
If you purchased Abulafia from the Mac App Store, please send a copy of your receipt to email@example.com and you will receive a complimentary six month subscription to Burning Slug.
Thanks for your support!