Just to avoid any misunderstanding (given the title of this thread): Freda is not an EPUB3 reader. It is only compatible with EPUB2 format. That said, I think the same is true of most other ereader programs. Also, it seems that most publishers are taking some care to ensure their EPUB3 books are backward-compatible - i.e. though supporting EPUB3 features, they are also work on reading systems that only understand EPUB2 format.
For those who are interested, I will post occasional updates about the Freda development roadmap on the forum, here
(that talks about the Windows Phone version of Freda, but in fact there is now only one development roadmap; the code-lines are merging).