Navit is currently included in the nonworking subtree of the webos-internals.org GIT tree. Though it is in the "nonworking" tree it is actually working quite well, but requires some modifications to the system.
Please go here to find out how to get the webOS-internals-PDK: http://www.webos-internals.org/wiki/WebOS_Internals_PDK
to compile Navit, "just" go to packages/nonworking/navit and do a "make stage".
This is just the start of this article, more is to come ;)