I have multiple computers that I use during my day. These computers are kept in sync with Dropbox (and the use of symlinks). In a recent update, it asked me for my license key again. No problem, entered it. Everything worked great. I switch to my other computer (made sure Dropbox was already synced) and on first load, ST3 asked me for the license again. I assumed because the 2nd computer just updated ST3, it was because of that. Switched back to computer 1 (after a Dropbox sync) and the license was asked for again.
It seems like the license key is now only allowed per machine.
I am syncing “~/Library/Application Support/Sublime Text 3/” into Dropbox.
Before posting, I made sure that the license was per-user and not machine. Based on sublimetext.com/buy:
ST3 Build 3054