"The basic idea behind open source is very simple. When programmers on
the Internet can read, redistribute, and modify the source for a piece
of software, it evolves. People improve it, people adapt it, people
fix bugs. And this can happen at a speed that, if one is used to the
slow pace of conventional software development, seems astonishing...
...The Open Source pages exist to make this case to the commercial world." - Introduction to Open Source - www.opensource.org
Replicant is an entirely free/libre operating system (including drivers). F-Droid is shipped with it.