Also Oregan has never 'thrown it all away', bits may get replaced but usually for a good reason (e.g. OS specific UI replaced with a generic HTML based one, mostly static HTML3.2/CSS1 layout engine replaced with a dynamic HTML 4/CSS2 one).
In reply to jess:
Most of the platforms the browser runs on has a GUI, its the one Oregan provides... As for integrating into the RISC OS desktop, this was tricky to do whilst still keeping the code portable, but was acheived for Oregano 2. The RISC OS GUI code is mostly the same in Oregano 3, it just required some tweaks to support new platform APIs and to handle changes in how elements are represented on the page (Mostly used to work out what type of element the menu was opened over so it can fill in the appropaite 'save' information.