Most things like this are not the core mission of the XSF, but in this case I think this aligns with one of the aims of interoperable standards - that is, client choice.
Google requiring all app development to go through them exclusively feels to me as if it's a barrier to client choice, a barrier to people choosing to interact with their services in the manner of their choosing.
I don't see this as being an "open source thing", therefore, but an "open standards thing", and the XSF definitely Has Views on that.
So I'm behind this one, both personally and with an XSF Member hat on.
Dave.