Must describe Open Source in 20 seconds (one slide of a presentation)

Question

I am doing a presentation, and I have one slide to introduce Open Source.
Slides automatically switch after 20 seconds, so I can't stretch.

How would you describe Open Source in 20 seconds?
(I don't speak especially fast)

Note: I mean FOSS. I know that there are tricky cases but in 20 seconds I don't have time to say "Free and Open Source", let alone explaining that sometimes you get to see the code only if you pay.

Answer 1

My question has got zero answers for a week, so here is my try, I would be happy if someone can find a better one:

Open Source software is free of charge and can be modified and distributed by anyone. It comes with no warranty, but major Open Source products such as Linux or Firefox are of great quality, developed and tested by large online communities. Some companies sell support for Open Source products.