Comment 2 for bug 1640370

Approach 5) could be as follows:
5) Like 4), but instead of linking to http://font.ubuntu.com/ufl/ or http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=OFL_web, it could link to an appendix page inside the e-book that contains the entire contents of such an external license page.

P.S. Approach 5) would end up adding 2-3 e-book pages per license, and could be considered a contamination of the e-books with unnecessary content. It would also entail English license pages in books in other languages, which could be confusing to many readers. And frankly, i don't think anybody has used such an approach for any e-book (or printed book).