Found it

8. We will pay you a royalty of 10% of all net income we receive as a result of our distribution of the book, in any form, printed, electronic, or other, or from the license or sale to third parties of any rights in a derivative work. For translated editions published by O’Reilly’s own subsidiaries, we will pay a royalty of 5% of net income. 9. If we include all or part of your book in another book that we publish, you will receive a pro-rata share of the royalties from that book in the proportion that the number of words used from your book bears to the whole book.

So it appears O'Reilly has handled the situation admirably. I can now sleep soundly knowing their authors are being fairly compensated ;-)

For anyone else still reading this there's lots more info on O'Reilly's process over at So You Want to Write a Book?

Thanks for an informative thread :).