OK, most users don't know. Most people know Firefox is free. But they understand it just as doesn't cost anything.

But des that really matter? More and more software is going open. More and more components of the software we use are free/open.

The average user knows that there is free (as in free beer) software like Ubuntu, Firefox, OpenOffice. Some of them even now what FOSS is. That is as much as those users can get from open surce. (OK there is something more like getting in contact with the community get part of it without being a developer)

People with developoment skills well most of them know that there are lots of open source software which they can use, and modifiy or learn from them. Quite some of them understand FOSS on a higher level.

Some goals like getting software, software we all depend on freely avaible to everyone (or at least good alternatives), also free to change, distribute and get part of it, well that goal of FOSS will success further without everyone and his mother knowning what free software is all about.

And then there is Wikipedia. Not exactly open source. But based on the same "Free" idea with a similar copyleft licence. Wikipedia does a pretty good job at bringing the idea to the masses. Nearly everybody knows that there is Wikipedia. That he is free to edit it. They all may not know the exact terms on which ground he can distribute it or change it and so one, but well it helps alout to distribute the idea of Free content/free software/free knowledge.