Ok, I know if I am Red hat or other giant and offer some support etc. I can be profitable, in fact, Red Hat is doing quite well.

However, what about a small company where I create a small program. e.g. an instant messenger for a windows or linux (just as an illustration) and I want to sell it.

But how can I sell it if it is free and everybody can download it?

Any advice?

I like the idea of FSF by Richard Stallman, however I am missing the way how to sell my software under GNU/GPL licence.

Any advice, how can I solve this problem? Any profitable small business software developers around with their opinion?

Any links or names of small companies taht I can look at and study their model of business?