Similar: Policy Plus: Group Policy Editor, but better! https://github.com/Fleex255/PolicyPlus

When clicking that link in Chrome I get a "The site ahead contains harmful programs" warning page with a bright red background.

"Attackers on github.com might attempt to trick you into installing programs that harm your browsing experience (for example, by changing your homepage or showing extra ads on sites you visit)."

How strange... I don't get it for other github pages.

Same here. Surprisingly, Microsoft* just allowed it, no problem. Edit: Also, Google doesn't trigger on https://github.com/Fleex255/PolicyPlus/ (note the trailing slash) but reacts to https://github.com/Fleex255/PolicyPlus (no trailing slash). Weird.

VirusTotal summary page says that it is detected by five different engines: https://www.virustotal.com/gui/file/dca4ecd769253d3b4a165a5b...

* Both Edge SmartScreen and Defender.