Some may be surprised by the merger, announced this week, of the open source Maemo and Moblin projects, given their architectural differences. Maemo targets ARM, while Moblin aims to enable devices with Intel Architecture (commonly "x86") processors.
Put aside that difference, though, and the projects are peas in a pod. Furthermore, given that the Linux kernel supports more than two-dozen architectures, can't open source app stacks evolve beyond architectural boundaries? Sure they can, and many have.