Also why did the Github owners agree to be paid in Microsoft stock instead of real money? There might also be arrangements in the deal for when and how much the sellers are allowed to sell the stocks hehehe.
I'm sure it was more money in the long run if the stocks hold out, mainly they do it because they don't have to come off the cash and the other party gains because they get more then the cash value but normally have a term of how long they must keep the stocks before they can sell usually a year or two.