EDIT: Found it, it's called Teleglitch: https://www.youtube.com/watch?v=iEnS4wPRETw
Actually, I've been working on the draft of part 2 when my Medium notification bar started going crazy - which is how I knew that something strange happened (the strange thing being an HN frontpage, apparently).
So, no worries, part 2 is coming soon (TM).
A lot of people (including me) practice extreme open-source for PICO-8 carts by licensing them as Creative Commons, which is easy to do - you just click a checkbox on submission.
This in turn leads to the best games being tweaked and remixed quite a lot - for example Celeste  (in my opinion, the best game on the platform) has at least one variant with a lot of new mechanics and gameplay .
 PICO-8 BBS: http://www.lexaloffle.com/bbs/?cat=7
 Celeste: http://www.lexaloffle.com/bbs/?tid=2145
 Perisher: http://www.lexaloffle.com/bbs/?tid=27694
Frankly if it requires an account I flat out won't use it in the classroom unless it is really simple and complies with COPPA (like Scratch accounts, especially the new classroom accounts)
There are a lot of people using it to introduce their children to game development and programming in general, and it's (supposedly) a blast for both them and the parents. I always felt that while our PCs have gotten 100x as powerful, they paid a big price in accessibility for actually getting stuff done on them when you're 10.
For adults, PICO-8 has just about the right amount of restrictions to keep you productive while still letting you create something worthwhile.
You're also free to sell your software, which you cant even do with unity without a royalty.
For $30 you can get a C.H.I.P computer, game pad AND a copy of Pico-8. So you can go retro on tiny hardware.
Although when I was working on a game for it, I didn't do much more than draw lines and fills on the screen :).
decide it’s impossible on the puny simulated CPU
Lua code runs at exactly the same speed inside the PICO-8 executable on a PC and in the HTML5 export on a mobile - in both cases much slower than in a standard Lua interpreter on my PC.
My guess is that PICO-8 is counting and limiting the number of opcodes the Lua VM is allowed to execute per frame, but that's hard to confirm.
It's certain though that everything you can do in code (from variable assignment to graphics operations like rectfill()) has a certain "cycle cost", and you get a limited number of "cycles" per frame - just as if it was a real machine.