It's not incompatible in the slightest. If I write software and give it to you only in exchange for money, licenced under the GPL, then I am selling software completely in agreement with RMS's principles.
Also, RMS doesn't insist on any freedom of end users to distribute without cost. Only on you not limiting their redistribution.
Now, that makes some licencing models impossible, sure, but those are hardly the only way to sell software.
Also, RMS doesn't insist on any freedom of end users to distribute without cost. Only on you not limiting their redistribution.
Now, that makes some licencing models impossible, sure, but those are hardly the only way to sell software.