I'm pretty sure a few tens of millions (lets say Nolen has 5% equity? I think give or take a few points, that's about right) for 4 years (generally the buy-out terms for a pair of golden-handcuffs) and the freedom to choose the direction in which TS goes (notice I did say "Lead" -- his role would have to be essentially Anders or Meijer's level for it to go through I'm sure) would be equally amenable for all parties involved. (I don't think you understand the freedom engineers at that level in MS get, especially post-Ballmer). Immutability sucks in TS? Oh well, here David, take 5-10 SDEs and do whatever you want.

MS gets the Clojure (and maybe more importantly the CLJS userbase), Cognitect gets massive reach (CLJS is subsidized solely by the licensing of Datomic by strict revenue), MS' corporate customers get Datomic. Just going by the direction MS has been in lately ("embrace & extend") under the new anti-Ballmer role, floating an offer of 300-500 million would be beneficial to everyone involved. Let's say there are conservatively 100k Clj(s) users out there right now using Clojure + Sun's JVM. At 300 million that's 3k per active developer acquired right off the bat. You'll lose maybe 10% of the users who live-by-their-Macbook-and-die-by-their-iPhone. Even at 600 million, that's still a cheap price to pay.

I'd say immutability is just about the only thing that's concise in Clojure/Script and everything else about it is a huge step backwards - especially the lisp syntax. Yuck! (Also IMHO.)