A friend of mine just did a masters thesis on free software
businesses.  She was specifically interested in how free software
companies differ from ones who do open source.  I haven't read through
it yet, but it might be interesting to a number of people on this
list.  From a quick skim, about half of it is a review of previous
research, and the second half contains her case study.

You can download it from http://ann.barcomb.org/.