[Mephisto]

Charging for it works on the mass market quite fine but not if you produce a piece of software for your customer alone (like a piece of finance software for a bank). Your customer wants to have this software so he is ahead of his competitors and he demands all IP rights of this work so only he can use it and decide what to do with it. And that you cannot do with software based on a GPL/GNU license as you have to make the software OS too. The demans of the OS and your customer are head on in this one.

Having said this, just to be clear, I'm a fan of the OS idead and OSS software. I just want to point out that there are some finer points to closed and open software in a business environment to be considered.