These are the most well-known activation scripts that many people trust. They are well documented and often recommended, with more than one contributor. Written in powershell, I believe that if they were malicious, some of the 46k people who starred the repo or 4.8k people who forked it would notice. That being said, you can only be sure if you read the code, which is luckily not that difficult in the powershell script case. I personally trust them, definitely more than I trust Microsoft itself :D