WiFiKill is a tool that allows users to disconnect devices from a WiFi network. It works by sending a "deauthentication" packet to the router, which kicks the device off the network.

The legality of using WiFiKill depends on your jurisdiction and how you use it. In general, using a tool like WiFiKill to manage your own network or with the permission of the network owner is likely legal. However, using it to disrupt someone else's network without permission is likely illegal and can be considered a form of cyber harassment or vandalism.

While WiFiKill may still be available on GitHub in 2021, its availability and effectiveness are not guaranteed. Additionally, the use of such tools must be done responsibly and within the bounds of the law. If you're looking for ways to manage your WiFi network, there are alternative tools and firmware available that can provide more robust and legitimate solutions.