At the end of the day, they're not quite competing for same market.
Also, fonts are not copyrighted! Only the data used to create the font, but not the font itself. Thanks to some very old laws (partly to do with not being able to copyright the alphabet) look that one up. :)
In a similar topic. The fonts renderers are copyrighted too. Maybe you remember some weird-looking unsmooth text on a java app running on the openjdk, that's why.
Last but not least. No, you can't create derivatives just because you want to. Derivation is very well covered by the law.
P.S. By "copyrighted", I mean whatever legal protection applies to these things, which may not be copyright law.
Just google it. If you find a counter argument, it's likely misinformed, you may have to dig to find the truth.
Any and all technical specs and software are copyrigtable, but not the shape of letters.
More I can't think of right now...