You should be able to create an API account with a classic noscript/basic (x)html browser (optionally with an email, and that could be an IPv[46] literal email address, you know, self-hosted & DNS free, which is stronger than SPF...).

Then to pay for, I should be able to redeem a code bought at my local and physical monetary terminals (no credit card info input on an internet able computer, even if elf/linux and lean classic noscript/basic (x)html web browsers) that to add credits on my account. Like steam. In my country, we even have codes for age verification only (you have physical age verification like when you buy alcohol from a [bottle] shop), much easier to crack down on abuse.

Another thing could be a public "anonymous", severely rate limited, API key for 'testing purpose' or very rare usage, or a noscript/basic (x)html web site (namely a real and honest web site) with ads (text/image/videos[<video>])... and with solid handling of HTTP refresh?

My main usage for AI would be coding. I am craving at mass porting C++ to a plain and simple subset of C code (it seems some people are getting reasonably good results, and it seems rust has a brain damaged syntax on the scale of c++), and assembly coding with very specialized code snippet.