Well, WebOS did it in secret and built their own walled garden of "web" APIs, sadly. That may or may not be why it never got traction. Either way, if you built a WebOS app then it won't run anywhere else today. With Firefox OS, Mozilla at least has used standard HTML5 everywhere that it made sense to. Granted, WebOS began its design a long time ago in web years.
> Either way, if you built a WebOS app then it won't run anywhere else today.
That's not very true. Any HTML5/JS app built for WebOS 3.0+ (when Mojo was depreciated, and Enyo brought in) can run in any browser; if it uses WebOS-specific API calls (most often used for notifications), then it can be wrapped in PhoneGap/Cordova and compiled for nearly any OS.
