Yes, you can publish an NPM package without having a repository linked to it. Technically you can inspect the source code using "Code" feature on NPM, but in this case it is minified. You can see a lot of stuff tho (ex: query used to inspect database, endpoints, etc...), but obviously it is not as easy to read as not bundled source code (not to mention you can use WASM, which is unreadable).
You mean npm? Of course. There's no requirement the software being published have source or even be open source. It doesn't even have to be javascript. You can publish anything you'd like as long as it has a package.json.