Imagine you created your very first app. You developed the concept, workedtirelessly on the key features, design, tested it and fixed the bugs. Themoment has...
Paid and FOSS are not mutually exclusive. You can always build packages yourself if you don't want to pay. A well executed implementation might allow some projects to drop or reduce their play store efforts.
Paid and FOSS are mutually exclusive. Open source and FOSS aren't.
But how, you ask? Free means having the right to do whatever you want with your copy including make copies and redistribute. Thus, how can it be free while demanding a payment before allowing usage?
That's why I said, FOSS Droid? Nah! Open Source Droid? Knock yourself out. I'm actually looking forward to supporting some of the developers of apps I love.
Free does not mean "no payment, ever". If the source code and build toolchain are openly and completely available, but prebuilt binaries are paid-only, it still satisfies the "free as in gratis" criterion.