GitHub does not "verify" these keys for legality; "verified" usually implies the key has been tested and confirmed to work by other users in the comment section
You have three paths forward:
Very Low. While some users report success with specific keys like XWCHQ-CDMYC-9WN2C-BWWTV-YY2KV for educational purposes, many repositories contain keys that are already blacklisted or were never intended for permanent retail activation.
This article will explain exactly what you need to know about Windows 8.1 product keys, why GitHub is being used for piracy, and most importantly, how to legally and safely activate your operating system.
If you cannot afford a key, Microsoft allows you to install and use Windows 8.1 indefinitely without activation. The only limitations: