What's up with this trend of doing stuff that only works on Chrome? On Firefox this works for a minute and then stops working.
I wrote most of our javascript on firefox. My firefox has no add-ons except the Firebug. Could it be one of your extensions? Have you tried refreshing it? Which version/OS?
We use howler.js to play the sounds. I have to say that I was a bit surprised to find Chrome/Safari/IE can play mp3 but Firefox plays ogg. I even had to submit a patch[1] so that howler.js can work on firefox under some weird edge cases.
My gut feeling is that those leaks are the "socket connections" that Firefox hasn't garbage collected yet. The demo you are seeing is using long poll so there might be some good number of socket churns.
FWIW, WebSocket support is high on our priority list. We just need to find the time to implement that.