The dev apparently used the RedReader app to test a "spoofing" method of access for a proof of concept, but they don't want to use that method either, because it would potentially cause problems for RedReader, which they didn't want to do:

If we do that, and cause a huge traffic boost under RedReader's name, it might lose them their exempt status. I'd like to avoid that if I can - there's no reason to paint a target on RedReader's back unnecessarily (an independent, non-commercial app), especially since the equivalent can be done with the official app without the same risks.

The real problem for Libreddit instance operators is going to be acquiring an API key. It doesn't look like it's an automated process like most other services - you have to fill out a form, which opens a ticket, and wait for someone from Reddit to get back to you.

I run an instance, and I'm not sure I want to go to the trouble. But I'll wait and see what happens.