I am glad to report my EPUB3 Validator add-on to Firefox is now available. A few details about it:

  • JavaScript only
  • not based on epubcheck's code at all, no Java code, does not rely on Java at all
  • my own xml content model validator
  • my own CSS parser and CSS Profile validator
  • Firefox >=12
  • Mac OS X, Windows, Linux
  • Free upgrades for life after purchase.

More information there.