"You'll note "price" isn't mentioned; it's actually OK to ask for money
for open source software, so long as you don't attempt to withhold those
freedoms from people who don't pay. As a consequence, if you're directly
distributing open source software, you need a business model that doesn't
depend on artificially enforced scarcity of the program. To focus on the
price is to remain trapped in the paradigm of proprietary software."