I was wearing the t-shirt that reads:

$> cd /pub
$> more beer

I encountered a person who said "I don't understand your t-shirt."
I tried explaining it by placing a Windows-like GUI around it, but
they responded with "I still don't get it."  They wanted to learn
more about the t-shirt, but I didn't have time to help them.

I was wearing the t-shirt that reads:  "Free Software, Free Society."
Three mailpeople were having lunch and one of them asked
about the t-shirt.  How fun!  We get to speak  briefly about
Free Software and "Free as in Freedom."  They found it
entertaining, but I doubt any of them will search the
Internet to learn more about Free Software.