(Note, this is more or less a place holder to start with.)
You'll want to follow the instructions on the webOS - Community Edition for the Touchpad page for getting your environment set up. The woce-build package has a new target called isis. This should compile WebKit, and all of the Browser components needed.
NOTE: WebKit is a 4GB download. You'll want to start this before work or before bed, and let it run... You've been warned!