Hi again Anna,
The only time the OFL or GNU GPL run into problems is when you want to embed the font concerned in a document. Embedding is different to just 'using' a font to produce a piece of text on a printer. If you supply someone with a document in some electronic form (say in a Microsoft Word .doc, or OpenOffice* .odt) and you want the recipient to see it exactly as you produced it, the font characteristics need to be embedded in the document in case the recipient doesn't have that particular font on his/her computer.
The open software licence generally permits software to be freely reproduced and modified but with the provision that someone who modifies it may only release their modified version free of any copyright restrictions. Where the software which 'draws' (either as a bit map or using vector graphics) a font is used in the context of a document which contains copyright text, the open source principle is theoretically being breached because the user is not releasing their document without any copyright restraints. This means that where a font is embedded (and you as a user won't always know if this has been done) then the user may breach the open software licence, unless the +FE exception has been applied by the owner of the rights in the font. This is a real technicality and no user, as far as I am aware, has ever been taken to court over this kind of licence breach, nor is it likely to happen. The problem is mainly one for the big companies who release the licensed fonts, and who are understandably keen to avoid any litigation.
Proponents of open software licensing tend to be purists which is why there are several different open software licences, each finely tuned to meet a particular need of its proponents. The Apache Open Software licence is described as a permissive licence
as it contains slightly more restrictions on how any derived software may be exploited.
So to summarise, interesting though all of this licensing is, you as a user do not need to worry the copyright implications of using any fonts which you have acquired legally, irrespective of the specific open software licence which comes with it. If you want, you can even use FontForge
to create your own fonts, based on more established font designs.
*OpenOffice was originally developed by Sun Microsystems as a free alternative to Microsoft's Office software. When Sun was bought by Oracle in 2010 there was much concern within the development community (who were not employees of either Sun or Oracle) that the new owner was trying to depart from the true open software licence model. As a consequence, some distributions of Linux (notably Ubuntu) stopped bundling OpenOffice and started using Libre Office
instead because of these concerns.