I guess you are right, PP, there seems to be GT-IP in our interposer. 
If not, why Bill/BB did not do this interposer by himself?
E.g. the interconnections by soldering with these ball points?! Ah, there are so many patents that meanwhile I lost the oversight.

But it was always a big asset of Poet's IP that it was not limited to GaAs!
Well, let us screen the last patents of Denselight, here we should find out!