Originally Posted by DiapDealer
Being listed as "embeddable and/or "editable" and/or "installable" has nothing to do with whether or not the font can work (functionality-wise) when embedded in an ePub. Those various labels only deal with the legalities of doing so.
There's at least one font property (OS2 version) that if set improperly can cause the embedded font to not work in ADE renderers, but other than that ... you can get most any font (ttf or otf) to function properly when embedded. It's just a matter of whether you can legally distribute it with your ebook or not.
I do know you can't just grab any font-file and slap a random encryption.xml file in the ePub and expect it to work. The encryption file is created at the same time the font-file is obfuscated and there are very specific urn id requirements in the opf file in order for ADE based readers to properly use encrypted fonts.
One thing that might work (but it's up to the owner of the font(s) is to subset the font(s). That way, you are not distributing an ePub with a full font file. What you are distributing is a font file with just the characters needed for that specific ePub. So say your ePub does not use the letter Q, the resulting font file will not have a Q in it. Not only does subsetting make the font file much smaller, it makes the font file not worth taking as it's not complete.