Open webOS officially got its 1.0 release today and while HP has only managed to get it working on a computer, the independent WebOS Ports team has a version of it up and running on a GSM Galaxy Nexus. After two months of development effort, the OS runs and can connect up to Wi-Fi, but complete support for phone functions, including SMS, isn't quite ready yet.
The biggest challenge is apparently getting full and proper hardware acceleration working, and as you can see in the video below that's something that will be sorely needed to make this anywhere near usable. The project is aimed at making a Galaxy Nexus with Open webOS a viable daily-use phone, but WebOS Ports tells us that it won't be publishing a full porting how-to for users until it's ready. When it is, expect those details to appear on the official Wiki.