[DotGNU]Business Models for Free Software

[Matthew C. Tedder]

Can someone recommend to me a good resource for various business models for
Free Software?

For vertical markets, consulting support obviously can work well but what
about a programming language interpreter or a game?  How could such things
possibly work?

A library like QT can be dual-licensed where the GPL can work to train and
popularize the library and money can be made when one wishes to sell a
non-free derrivative program.  In an ideal world, we would prefer that these
derrivative works also remain free.

At present, I GPL what I can but am often blatantly forced to write non-free
software.  I don't like it.. But I see no answers.

--Matthew