As per https://www.linuxfoundation.org/about/, the Linux Foundation pays the salaries of Linux and Greg K-H. So Microsoft do indeed indirectly pay for a part of their salaries; along with AT&T, Fujitsu, Hitachi, NEC, VMware, Accenture, Juniper Networks, Toyota (the list of corporate members is at https://www.linuxfoundation.org/membership/members/), plus all of the non-student Individual supporters (https://www.linuxfoundation.org/membership/individual/).