Not often do we enter a Linux Distribution and truly mind the “non-free” software that is included (Linux Mint, cough). Although this non-free, and proprietary software is great and often does what we need to do, it is against the vision of GNU/Linux, namely Richard Stallman. Whether or not you agree with this philosophy, is entirely up to you.
So really, what is “free software?” I’ m sure you can google around, but I’ll brief you in short. “Free” software is devoid of proprietary code, allowed to be shared freely, modified changed, to allow collaboration and betterment of the software at hand. This not necessarily means 100 people commit horrible changes to a piece of software, rather it gives any developer, or user, the ability to change the software on their machine, and if they think it is worthwhile, suggest the code changes to the upstream developer (the original creator), to modify it permanently.
So what is “Open Source” then? As GNU puts it, ““Open source is a development methodology; free software is a social movement.” For the Open Source movement, non-free software is a suboptimal solution. For the Free Software movement, non-free software is a social problem and free software is the solution.”” With Open Source, sure you can get the source code files, but often carries restrictive licensing, or restrictions on “freedom.” Free Software’s philosophy aims to break those chains, and allow a sort of “1st amendment right” on software.
The Free Software Foundation maintains a good list here of such “free” distributions. The spotlight right now is on Trisquel GNU/Linux 6.0. Feel free to give it a try! Essentially, it is a stripped version of Ubuntu, with only “free” software. The joy of Linux is you are not confined to one “OS.” There are so many to try! Choice is power folks.