http://userlinux.com/white_paper.html

" Database: MySQL with non-GPL libraries. This departs from the standard
MySQL release in order to facilitate commercial development and
distribution without forcing the user to purchase a MySQL developer
license. Pay MySQL for training and service. I am not a database pro,
and * will listen to argument about the merits of other database servers. *"

I think we have to respond if they could include firebird in user linux .