A speech hold to Free Software Briefing WSIS-2005, Richard Stallman explains what is free software, open-source. Although he came with aluminium foil around his badge, saying he can be tracked by this, he's motives are very well-founded. Most software runs in our computer without knowing whether or not collect information about you for a reason "well founded".
Part I of the meeting:
Part II of the meeting:
More about Richard Stallman can be read on his wikipedia page.