What is your favorite Linux distribution and do you approve of GNU and open source?

Commercial with Support Server RedHat Enterprise Linux (RHEL)

Non Commercial use as Server CentOS

If you like to cut down your linux distro, create a distro for a lot of flexibility use Debian

Highly user friendly desktop Ubuntu

http://distrowatch.com/dwres.php?resource=major can answer your question. 

Scientific Linux.Its a valid distributor of Linux OS.

Centos - For more info please visit http://goo.gl/NcbKsf

And yes I approve and prefer GNU and Open Source