Hello, I just downloaded and installed Sonic Pi 3.0.1 on my Apple Mac.
I received the message that “Sonic Pi can’t be opened because the identity of the developer cannot be confirmed.”
I posted a message on Google Groups and then seeing that the message had not shown up yet (awaiting moderation, perhaps?), I then consulted Google (Yeah! I know, it should have been the other way round!).
The answer, for anyone else facing the same issue, is to locate the app in the Applications folder of Finder and press the Ctrl key before double-clicking Sonic Pi. Then confirm that you want to open the app.
This “in_thread” forum looks much better than the Google Groups. Happy days!!