Originally Posted by Jellby
Well, according to the ePub 2.0.1 spec
Any font files included in an OPS Publication must
be included in the OPF manifest
with appropriate media type (application/vnd.ms-opentype
for OpenType fonts).
Note that passing epubcheck does not mean everything
is fine, it just means that it passes epubcheck. (Likewise for FlightCrew.)
Regardless, it's ePubCheck that most publishers go with. So it epc says it's OK, then it's OK for them.