As of 2024, Forza Horizon 2 is not on Game Pass. Because it is delisted, Microsoft no longer offers it as part of the subscription.
: Files titled "license key.txt" or "serial.txt" from unofficial sites are a common way to distribute viruses or ransomware.
The license key.txt file is a plain text file that contains the license key for Forza Horizon 2. The purpose of this file is to store the license key in a readable format, allowing users to easily access and use the key to activate the game.
There is no such thing as a working license key generator for a delisted game.