> How big a share of the desktop market do the BSDs have compared to Linux? I imagine it’s quite small, unfortunately.

Good stats are hard to come by, but the Linux : BSD ratio is probably no larger than the Windows : Linux ratio (which is actually running relatively low these days--Linux seems to be closing in on ~3% desktop share). That puts the BSD overall in the 0.01% range, which is really too little market share to accurately measure.