They didn't put WebOS on an iPad and no one has been able to verify this claim, ever. Now the apps, mostly, are javascript and css. Most apps you could run through the browser on an iPad and that is how WebOS development is done.
In fact you could start the WebOS emulator, designate a port to connect over and open your favorite browser to the IP and port of the emulator. This is how actual development is done as defined in their SDK.
Most of the people posting this ridiculous link don't know what they are talking about. Anyone can run a webos app in a browser. No one has been able to run webos outside of webOS devices.
The original article I read reported that the webOS userland was loaded in MobileSafari and it ran at more than twice the speed. Screenshots of it in action were also given. Granted, that is easy to fake.
I'm not familiar enough with webOS to know how much of the userland is written in HTML/JS/CSS, but it doesn't seem completely inconceivable. Even if it was just benchmarking of apps running standalone at more than twice the speed, that alone is pretty significant.
WebOS gui is written in javascript with hooks into the hardware. In fact its so easy to modify you can download the ipks from preware and see that they are shellscripts of patchdiffs to different parts of the system. Want to turn on the flashlight from the menubar? There is a JS function call in the system library for that.
My first exposure to it was disabling the CDMA radio, from javascript, and enabling wifi. I was using a Sprint Pre for development in a country where only GSM exists. To get past the initial setup screen I configured the system to use wifi instead of GPRS.
The great thing about WebOS was it was open in the literal sense (unfortunately, not the license) you could modify every aspect of the system using javascript and CSS. There is nothing else like it in the world. Not Android, not WP7 and definitely not iOS
WebOS is slow on TouchPad due to large amount of logging done in the background. There are patches available for WebOS which decrease / disable logging making the whole user experience quite snappy. The main culprit for slow performance are the logs not the hardware.
The problem with the ToughPad was that the hardware was appallingly slow.