The GPL font exception allows the font to be embedded within a digital "document" file without requiring the "document" itself to also be shared with GPL.
Now I wonder, what is considered a "document"? If the GPL+FE font is embedded in a software to render a user interface, the software can be released with a non-GPL license?
Seek legal advice in your jurisdiction.
Seriously, because the cases and laws are all over the place...
I perviously delved into the question of font licenses in Can I use a @font-face of "Courier New"? - and while much of that answer is about the font Courier, it exposed things like 'typefaces aren't copyrightable in the US'. Much about this is said in Policy Decision on Copyrightability of Digitized Typefaces from 1988 which states that the Copyright Act of 1976 rejected the ability to copyright a typeface:
The decision in Eltra Corp. v. Ringer clearly comports with the intention of the Congress. Whether typeface designs should be protected by copyright was considered and specifically rejected by Congress in passing the Copyright Act of 1976.
There are other forms of protection that may be applied to typefaces, such as design patents (such as the font used by Coca-Cola) and names may be trademarked. However, the font may not be copyrighted... at least in the US. The files that specify the font may still be under copyright, but this appears to suggest that one create another font that looks the same (as long as you aren't working from the original) the font and reimplement it and copyright wouldn't protect against that.
And that said, one should also pay attention to Adobe Systems, Inc. v. Southern Software, Inc where it was found that Adobe did have copyright over a font that was implemented as a scalable representation rather than a bitmap.
And all of this is applicable only to the US law... other countries do allow for copyrights on a font face.
So... talk to a lawyer. There are a number of different findings and laws and such that all intermix in this area that make it impossible for someone who isn't familiar with the law and intellectual property to navigate.
Further reading and referenced works::
In my view the definitions would be those used by the relevant copyright law. The law is quite careful about definitions of things, and if you had a font embedded in a work that fitted the definition of "program" then the law regarding "program" would be what would apply. Trying to call a "program" a "document" would not help.
As always, if you make no money out of it and harm no-one then just do your best, acknowledge the work of others and don't worry too much. If you distribute something with GPL in the mix you will probably have to distribute your source code and if you don't, prepare for some unpleasant questions as to why not.
if you make money out of your product or services and/or if you may cause damage to someone or compete with someone who does, then you must take competent legal advice. That won't protect you, but it will warn you about the risks and possibly help to mitigate them. You are at risk, even if you don't realise it, and the more money you make the bigger the risk.
