Here's my perspective as a long-time (3+ years) power user/plugin developer:
>>> import this
The Zen of Python, by Tim Peters
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than right now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!
On the topic of whether Sublime is still alive: yes it is. OK, we go through fits and starts of dev builds being released one right after another, then a quiet period, then more builds, etc. We're obviously in a quiet period now, but I'm sure Jon is still working on the project. ST4 is in the planning/architecting stage at the moment, while ST3 final is still waiting to be released, so he has plenty to work on. He has always been rather non-communicative on this forum, except in the hours and days immediately after a dev build when dealing with major bugs. He is very much aware of the SublimeTextIssues repo on Github, and I'm sure it figures into his planning. Some members of this forum are in direct contact with Jon, and have periodically reassured us that yes, he is still alive and still working on Sublime.
Could the communication be better? Absolutely. Should Sublime be made open-source? IMO yes, but it likely won't happen, at least for a while, unfortunately. Should you switch to Atom? It all depends - does it fulfill your needs? Do you mainly use the languages it focuses on? Are you comfortable with its design and API architecture? Do the available plugins and extensions meet your needs? It's all up to you. Personally, I don't prefer Atom, because it doesn't meet my needs (no equivalent of SublimeREPL, confusing API, package manager implementation is poor, etc.) while Sublime mostly does. That may be different for others. I chose a long time ago to pay for Sublime because it was the best editor I've ever used (which is saying a lot) and I wanted to support future development. I would make the same decision today in an instant.