I have an application that uses a version of sox compiled with lame for mp3 support. The application won't generate enough revenue to justify the $15000 a year minimum license fee for mp3 processing. I looked into other free formats like ogg but does not appear to be as ubiquitous an industry standard (never heard of an ogg player). Can I have a link where the user can download their own version of sox for the processing rather than distributing it?
Update 2014-04-27 As pointed out in the comments my answer is flat out wrong, and I am refering to distribution rather than royalties associated with MP3 software. There does not seem to be any minimum revenue Before you need to pay up, and the annual minimum fee is $15000...
Please refer to: Royalty rates
Original (invalid) answer
The $15000 a year is a lot of money, but it only applies if you already are making >= $100000 on associated revenue:
"However, no license is needed for private, non-commercial activities (e.g., home-entertainment, receiving broadcasts and creating a personal music library), not generating revenue or other consideration of any kind or for entities with associated annual gross revenue less than US$ 100 000.00." Source: http://mp3licensing.com/help/index.html
Maybe you were already aware of this, but in case not i thought this might be helpful..