As said in the Disclaimer, you have to use a custom version of nwjs.app.

It can be downloaded on the alexeyst's node-webkit-macappstore repository (direct link).

Package your app by following the regular NW.js procedure (if you don't know how to do it, check the official documentation page).

Roughly, you have to:

• Rename your app root directory (the one containing the package.json file) to app.nw
• Move this directory to nwjs.app/Contents/Resources
• Rename the app to what you want - let's assume it is YourApp.app

To ensure proper validation, you have to check those steps:

Delete the FFMPEG library:

rm "YourApp.app/Contents/Frameworks/nwjs Framework.framework/Libraries/ffmpegsumo.so"

Delete .DS_Store files that may have been generated when you were working on your app:

cd YourApp.app && find . -name "*.DS_Store" -type f -delete

Remove the crash_inspector file, if it exists in your app:

rm YourApp.app/Contents/Frameworks/crash_inspector