The project is based on a fundamental insincerity, which makes me suspicious. All material about Urbit makes a big point of their minimal spec, again so in the linked piece: "The spec fits on a T-shirt and gzips to 340 bytes."

What do people expect when they read a thing like that? I don't know about you, bit I'd expect that I could ignore the obfuscated strangeness of their higher level languages etc and just implement stuff to that minimal spec.

So you expect you can do that. But you can't. That minimal spec might as well not exist; you can't just read it and go on to implement, say, a programming language on top of Urbit.

"But you can!" you might object. Try it. Read nothing but that spec and implement, say, a tiny BASIC on top of it. Compile some simple programs. Run them. Now, what happens? Nothing, for now. But look, my processor core is heating up. Something must be happening! Just wait. Wait. Wait. No, still nothing. Wait some more. Just a few years, maybe? No, still nothing (except heat). Etc.

So no, that elegant spec doesn't give you anything but a way to heat your computing cabinet.

Realizing this, I put Urbit in the "suspicious, may be a con" bin. Hasn't escaped from there, yet.