And netfabb if also free as well as commercial.

Apparently the new commercial one is the dog's bollocks - well according to autodesk at the tct show anyway :-)

Also simplify3d is NOT proprietry, it's commercial.
It's not tied into any manufacturer or machine. You need to change that heading to Commercial or paid for.

Examples of Proprieitry slicers would be things like: Flashprint and whatever the hyrel uses. Ie, software that is specific for a particular brand of printer.