[rolandog]

I'll go try to answer these for myself, but — using the "both things can be true" argument — I have a couple if follow-up questions:

1. Do they still require transfer of copyright to IEEE?

2. Or, conversely, do they publish public domain articles?

[A_D_E_P_T]

1. No. "TechRxiv offers several Creative Commons licenses, all of which permit you to retain copyright of your work. You do not need to transfer your copyright to TechRxiv."

2. Preprint servers aren't really for the publication of articles that were already published elsewhere. But you can have an article published on TechRxiv peer-reviewed and subsequently published in an IEEE journal -- or a non-IEEE journal, for that matter.