I'm working at Deno, mostly on the open-source version so I can clarify a bit. The open-source code of Deno runs in Deploy, but some APIs are disabled and others are adapted for cloud use (ie: Kv works in CLI and Deploy, but is distributed on Deploy).

Under the hood Deno Deploy is just Deno with scale built in. It's obviously not a simple soundbite but I recently built the new Deno.serve API implementation and the same code effectively runs in the CLI and Deploy modulo what's necessary to get it working in the Deploy environment.