[Trisquel-users] why does the free software foundation reject mp3?

[svhaab]

Is it the codec? Is it the license? Is it the software that plays mp3 files?  
Here  
https://www.iis.fraunhofer.de/en/ff/amm/prod/audiocodec/audiocodecs/mp3.html  
it says, that patents are stopping.
Does that make a difference?