I think the end-goal should be to have a close collaboration with EleutherAI, who already have an open-source alternative to the Copilot model. It's called GPT-j.

ελευθερία is a greek word that means Freedom. EleutherAI are open-sourcing language models.

The problem is that there are very few people within EleutherAI using emacs and few people who can help. 

If you'd please excuse my speculative musings, emacs has 40 years of design waiting to be augmented with GPT3 and I believe that emacs is way ahead of the competition. It's a gold rush really.
Name a package and I can name an augmentation. GPT is orthogonal to coding the way macros are orthoganal to functions.
emacs has tens of thousands of packages which are essentially just a skeleton for GPT to become the body, so this is why I recommend fostering a prompts repository right now.
For example, take nano-emacs and turn it into the best writers environment ever.
Take 'erc' and make it the first IRC client to automatically translate all messages into any type of dialect -- French, Klingon or Pirate.
Company-mode + GPT = Copilot.
Org-roam + GPT = A multiversal prose editor (https://github.com/socketteer/loom)
Org-brain + GPT = a mind map, which automatically generates and suggests nodes, then lets you talk to a chatbot tutor on any weird topic you can think of.
VSCode literally cant do this stuff because it doesn't have the structure created yet.
The biggest bottleneck to unlocking GPT-3's potential is the latency of the human imagination to cope with anything that departs from realism.

I'm a little overwhelmed building Pen.el, but EleutherAI has been very helpful in supporting my project in guiding me to the right projects.

It is, in my humble opinion, still important to foster a FOSS prompts repository in the meantime.