I'm an opensource programmer and I program and mine for fun. I get money for programming on my job.
But I also think that everybody is free to ask whatever they want for their work.
There are "professional and highly skilled developers" who program for free (like myself) and bad programmers who ask for money :-D
I don't think we intend to ask for mining fees or anything like that. But we would like to see nVidia users have a bit of an advantage in the mid term at least. Because if everybody mines faster, there is no benefit for anybody.

Hence we would like to take the time to make nVidia specific optimizations (e.g. I intend to make heavy use of the warp shuffle feature for Groestl which does not currently exist in OpenCL). And when needed we may also decide to do a binary only release - requiring us to find workarounds to stay in compliance with GPL terms.
Christian