The Sage git repository (my current copy) is worth $192,937,447 according to David A. Wheeler's SLOCCount.
SageMathCloud has 68,652 active monthly users, as of September 2015, according to
http://sagemath.blogspot.com/2015/09/what-is-sagemaths-strategy.html
William "Dr. Evil" Stein is thus stealing 68,652 x $192,937,447 = 13 TRILLION DOLLARS from the Sage developer community, every month.* This figure does not even account for the value of Sage's dependencies.
This is of course very upsetting. However, it also suggests a viable source of funding for Sage developers (with plenty of precedent in the intellectual property industry): start suing others over lost potential profits. Myself, I'm modest and would settle if I get just a few million dollars.
Fredrik
* I could not find RIAA arithmetic implemented anywhere in Sage, but ZZ was adequate for this calculation.