THIS IS JUST MY OPINION NOT FACT.(1)
Quoting from unix for dummies:
Linux is made available under the GNU General Public Licence version 2.
You can copy and distribute linux and other gpl software and you can charge for it.
But anyone to whom you distribute it has the right to give copies away for free,
And you must include the source code or make it available in the distrobution.
I don't know if there is any non GNU (GPL) software on the disk, if there is it will probably be subject to copyright.
Follow these rules and if you want to charge for it and people want to pay you for it, there isn't a problem.
Mandrake has a partner distrobution page @
http://www.mandrakesoft.com/partners
footnote
(1) Since it is my opinion it is probably correct, but that is just my opinion. see (1)