not freeware,
PS6 about 600$
Mudbox about 800$
but ... you know.. you can easely get it for free if you know how. try this soft for free, and then if you like it, and you will plan to have some profit from using this progs, buy it. I dont like the idea to buy such expensive soft for some kind of hobby, and use it like once a month without any profit.
Google mudbox, this is the first thing that pops up
even on their own website
http://www.autodesk.com/products/mudbox/free-trial
maybe you don't have windows 7?
While the Autodesk Student Version software incorporates all the functionality of our professional licenses, it may not be used for commercial or for-profit purposes, as more fully described in the License and Services Agreement. Term-based licenses of Autodesk student software are not eligible for product upgrade or migration to a commercial license.