NUURBY only ever talks to the instance URL you configure — nothing is sent to any third party. Full details in the privacy policy.
Browser extensions can't do real network scanning — browsers deliberately block that. The NUURBY Network Agent is a separate local app that solves this properly: it runs on your machine with real OS-level access, discovers devices on your network, and pushes results straight into your Asset Inventory.
Currently source-only — building the double-clickable app requires a few one-time setup steps (covered in its README), separate per platform. Same scanning engine this platform already uses either way.
Both platforms currently ship as one combined source download — it contains the build files for whichever OS you're building on (setup.py for macOS, agent.spec / build_windows.bat for Windows). Full instructions in the included README.