Google just released the Android 2.1 source code to the public, but there aren’t a whole lot of options for custom ROMs. There is one, though, that includes multitouch, as well as a bevy of other small hacks. Back up your important info before trying any of this before you try any of the tricks. Back to the main post: Rooting the Nexus One can void the warranty, but rooting the phone can also cause data loss. The trick is to unlock your phone’s bootloader, so you can boot from whatever you want.”]
Source: https://gizmodo.com/how-to-hack-multitouch-onto-your-nexus-one-5455442