Based on a number of opened issues, it seems that the "Is an extension" field might be causing some confusion as to its meaning. Without providing too much detail, I'm still thinking that we could attempt to clarify that it's referring to either of the *browser* extensions.
Given that the mailing list has now been closed, see [bug 1340296](https://bugzilla.mozilla.org/show_bug.cgi?id=1340296), and that there's no weekly meetings any more, we probably shouldn't mention either of those in CONTRIBUTING.md.
Instead, let's just suggest the IRC channel as a means of communication here.