Change Tactics, PLEASE
I respect the FSF's mission, but think that this tactic is misplaced.
GMail is essentially a client-server application. The client is written in JavaScript, and the server is embedded in Google's back-end infrastructure. The protocol between the two is proprietary and undocumented.
Google wrote its own email protocol because POP and IMAP, while standard, do not meet the needs of what people really want to do today. By throwing out the standards, they build a better end-user experience. This is not so different from the way Microsoft built its own proprietary email protocols in the past.
The most valuable thing the FSF could do here would be to:
1. Get people talking about standardized advanced-functionality email protocols, beyond POP/IMAP. Then we could all start building advanced email clients and servers with the great features that GMail has.
2. If they're going to prod Google to open something up, they should be asking for the protocol, not the JavaScript client. All they're going to get from the client is a bunch of GUI and network interface code that gives little insight of the actual heavy lifting going on behind the scenes. But realistically, the protocol probably won't give much more anyway.
The GMail back-end is what would really be interesting. But I sincerely doubt Google would even THINK of open-sourcing the GMail back-end. FSF should just start a project to write that kind of stuff itself.