WTF is this?
That’s the sign that you have received all the updates that you agreed to when you purchased the software.
Now you get to use the software you have for the rest of your life at absolutely no charge. I know this is a very frustrating limitation.
Change the wording to “Subscription Upgrade Required” and I’d be fine with it.
Well, this implies that you’re fine with the concept, but all butt-hurt about the wording. Chill out man, jeez. I see there’s a professional response from Sublime HQ above… in my mind though, it contained all my favorite Straya slang, and as much as I would have enjoyed reading THAT, at least the boys down at Sublime can take solace in knowing that we’re all THINKING it. 
Sublime is still my daily editor after about, shoot, 15 years or so? I’m sure I’ve bought it multiple times. The idea that a team of people work on something for 15 years without compensation is crazy.
Imagining that sending emails to Tim Cook is a productive use of your time is farcical, but that data does provide everyone here excellent input in how seriously to consider your concerns, so it’s appreciated.
Talk about a sentiment that evokes the gag reflex.