Windows Defender found and quarantined the file FileWatcher_NativeApp_1.0.1.exe, saying it was a virus: Trojan:Win32/Occamy.CAF.

It appears to be a false positive, and this was confirmed by Microsoft after submitting the file for review to Microsoft Security Intelligence.

So this app is safe to install.

Finally a replacement for the Auto Reload extension (which no longer works with current versions of Firefox). A little more complicated to set up (using rules), but works well and has the added benefit of reloading files that are run through a local development server.