I too have been mystified by R's licensing. I actually don't see how anyone can ship a commercial product using R in its current form. At very least you're in a legal gray area, at worst you are involuntarily open sourcing your product. Not that there's anything wrong with open sourcing a product, but I think there's an enormous potential issue that could foul up a lot of people down the track. The best discussion I have seen about this pretty much ends up with uninformed speculation. For now, I take the policy of "explore and prototype in R, build the real system in something else". Fortunately the flaws and limitations of R as a language make this a sensible choice for a host of other reasons as well.