1) If there is an avenue for zerocash developers to work more closely with bitcoin, what does that look like? Does it mean that @imichaelmiers & @matthewdgreen (on github) could be invited to work directly on the bitcoin protocol, and have the ability to make commits along with yourself, Gavin, and others?
I've been hired as an advisor to the Zerocash team, and likely will be doing development work as well. There's not very much need for Zerocash developers to be working closely with Bitcoin at this stage, although in the future that may change.
As for "ability to make commits" - there is no need to try to "grant" that ability, and in any case, those with commit access the
https://github.com/bitcoin/bitcoin repository have no special powers in practice. If anything I personally would consider that access an annoying burden, not a useful thing to have.