PC version Fans have made a PC version. Some are still early, so read the project page first.
Fans took Forza Horizon 1: ReImagined apart and rebuilt it so it runs natively on a computer, often with widescreen, higher frame rates and mods. Here is the project we know about:
Forza Horizon (Xbox 360) natively on PC, rebuilt around the modern Horizon experience: shared online free roam, leaderboards and rivals, 120/144 fps, and a self-hostable online server.