Last week I talked about our plans around Mac build signing. In it, I said that I intended to have signed dep/try builds by the end of last week and signed Nightly builds early this week. Unfortunately, shortly after publishing I realized that due to some complicated infrastructure reasons, we couldn't turn on dep/try build signing prior to Nightly. However, I'm pleased to announce that all the necessary work for Mac builds signing is landed and in production. From now on, mozilla-central based builds will be signed. As other branches merge the necessary patch, they will be signed too. Nightly updates have been disabled for now, to give QA a chance to verify everything. Nightly updates should be re-enabled sometime tomorrow. This should be an invisible change to everyone, but please file bugs on any issues (especially those related to new installs or updates) and cc me (email@example.com).
Additionally, I want to correct one thing in my previous post. I said that applications 'will not run on 10.8 unless the user has allowed “applications downloaded from anywhere” to run'. However, it has come to my attention that this isn't entirely true. You can except specific applications from this policy if you ctrl+click the application and hit "open". This works for unsigned apps, self signed apps, and those signed with a Mac Development certificate.