..actually, I should mention that although most of the library is still GPL, the core module is now under a permissive ISC license. So if you're doing non-GUI or audio stuff, you can use many of the core classes for free.
Jules I am a real fan of your work, you are an inspiration - thanks for your response! Reading iain's comment again - I think he knows it is GPL already but for commercial users he's concerned that they would have to GPL their code to get updates if something unfortunate were to happen.