Hey, I'm the lead developer of Kylo. This post came through a Google alert and I thought I'd butt in and say hello.
I'd love to see Kylo ported to Linux for the Raspberry Pi. Contact me through the kylo forums or via Github and I'll do my best to support you.
We actually had a desktop linux port underway several versions ago, but we ran into some issues and wound up abandoning it. You're right that because Kylo is based on the XULRunner/Gecko library, it's already mostly cross-platform. We just have a couple components that handle mouse events and the on-screen keyboard that need to be ported. Then there's general quirks and discrepancies that need to be resolved (I think we ran into things like a full-screen veil that wound up solid black). And of course, the build script would need a lot of massaging, but you can probably get started without it.
Good luck! And thanks for checking out Kylo!