This three project provides similar functionalities, say desktop environnement api.
How :

• OS.js is split into a node.js server and a web application communication via remote HTTP
• NW.js insert node.js into chromium in a unique process
• Electronjs split into node.js and chromium into distinct processes communicating via local IPC
• Notice that OS.js can run as a standalone web app (without any server backend), and even be installable PWA and fully offline

OS.JS is not widespread ; NW.js and Electronjs have comparable wide acceptation.
(NW.js and Electron come from a same project, node-webkit, before little diverging)
(NW.js focus on a web application able to access native services via node.js;
Electron focus on a background nodejs application able to open web windows)

I think that we must tend to evolve OS.js toward a unified API matching both NW.js and Electronjs
(We could aloso consider Apache Cordova...)
So we could provide OS.js in following favors:

• client/server web app (optionally installable PWA, sometimes requiring network connectivity)
• standalone web app (optionally installable PWA, optionally fully offline)
• desktop ligtht single process application (based on NW.js)
• desktop robust multi process application (based on Electronjs)

So we could gain in popularity.

That is for OS services.
Next step would be to provide unified UI Toolkit
(either only Web HTML5, or unified with NW.js/Electron, or maybe even more compatible like Ionic)
(I name Ionic as an exemple, I dislike it, because even if now publish under MIT license, it tends to be commercial)
(UI Toolkit is another concern, and should be independent of OS)
(an UI Toolkit ecosystem will never converge in a common api)

((For now, I'm working to provide a standalone OS.js prototype which we could be configured dynamically through some configuration application, like installing packages from npm cdn, and serving files from OS.js filesystem, and running application edited into OS.js via by example ACE Edito... But I'm few avaliable, and I also try to work from locally file served which is awkward...))