"Joy" -- I feel like I spend all my time bookkeeping -- which is about the least fun thing imaginable. The guarantees keep me interested, but just barely at this point.
1. Well -- unless I misunderstand, they use STM to emulate a GIL (while actually letting stuff be done concurrently). Which means that it will still be a bit of a hodgepodge messy disaster.
2. I can't speak for Dropbox, but I worked in a shop that bet their future on Python -- and we spent a good bit of effort looking at PyPy ... it was a nightmare if anything went wrong -- a horrific impossible to debug mess.
3. Yep, I added Python to my "won't work on" list of languages (with Cobol, Progress and MUMPS).
Git already has this, it is already a thing, since 1.7.9. I can sign my commits, you can validate my signature, if we both care, it is out there already.
... you can sign your git commits with GPG, which is a hell of a lot better than "technically signed" via random internal LDAP and implied relationships.
Git has an intentional separation between author of a commit, and the person who signed-off on it. So if you hired an outside contractor to work a little bit of code, he could write it, send it to you, and then an internal person with a GPG key would review it and sign-off on it. It would retain the original author (contractor) and it would retain the person who put it into your code and "signed off" on it.