The punchline seems very ambiguous, at least for me. NextJS is most widely known for serverside rendering and prerendering React sites. How that maps over to CLI tools, I'm not sure.
Looks like the primary similarity is that to get started with Opaline you simply put some (specifically organized) files into /commands like you would do for NextJS with /pages
Looks like a fabulous idea to abstract away the boilerplate parts of building a cli tool. Looking forward to use it in a side project soon.
What's that terminal status bar you've got at the bottom of the screenshots?