This is released under GPL-2+, see COPYING and notices in source files. Files src/object_heap.[ch] have an additional MIT (Expat) license notice with Intel copyright. Please update all ebuilds of the package.
Really add MIT? As it is GPL compatible, I'd say "GPL-2+ MIT" is practically the same as "GPL-2+" A large number of packages would have to be changed if MIT must be added here.
I'm trying to be as precise as possible. ;-) But you're right, this one is a border case, as the two files in question have both a GPL-2+ and an MIT notice. So go with "GPL-2+ MIT" or "GPL-2+" alone, it doesn't make any practical difference.
Fixed.