Hi
I can’t find PLEX in add-ons list in aTV Flash black
Help
I actually came here to see if it had been updated to 5.2…apparently not. If you install 5.0.1 on your ATV Plex will be available. You can do that through seas0npass
Here is the latest update from thomashw – he is working on it!
http://forums.plexapp.com/index.php/topic/51259-plex-0110b2/?p=379978
I just sent him a PayPal donation to show my appreciation. You can go here to do the same. 
And in the meantime I am using the PleXBMC plugin inside XBMC. It’s okay, not great, but at least something usable while we wait for an actual Plex app!
thomashw, on 04 Apr 2013 - 21:38, said:
Hi guys, I'm sorry for the lack of updates. I have slowly been working on getting Plex to work on the new firmware, but unfortunately it literally means going over each file with a fine-tooth comb and and since the project is large it takes quite some time (and it's not the most enjoyable task in the world!). If you're interested in how we have to do things now you can look here and read the README: https://github.com/lechium/HelloWorld_ATVBlack6
Also look in the Classes folder at the .xm files - I have to update all of the Plex code similar to those .xm files.
I don't have a timeline for when it will be done, but I hope you knowing I'm working on it gives you a bit of peace of mind.
As for other developers helping out, they're certainly allowed. I know at least one developer was given access to the repo as I was discussing how we should coordinate working together over emails, but unfortunately he didn't reply and I haven't seen anything from him (this was about 6-8 weeks ago).
I'll try to pop back in to answer any more questions you guys have. Let me know.