Let's break this thick glass once and for all. Patching free operating systems like GNU/Linux with proprietary pieces is not mandatory for world prevalence. And it sure is not mandatory for basic functioning of the system anymore either, so you can't exactly use the "RMS used proprietary UNIX to build GNU" argument anymore. We have the complete Free OS. We have three of them. Now we have to go further and build a market around them, on our own or with help of others. We have to do it either way.
1. Mixing oil with water: the prevalence of a mixed operating environment