From time to time other projects uses some parts of NetBSD in their systems (or even use NetBSD as a base for it). The latest news came from Genode project. They took an interesting approach to add support for NetBSD ffs, ext2 and other filesystems supported by NetBSD itself by integrating rump kernels which allow to load NetBSD subsystems and drivers on userland (kernel driver virtualization). Unfortunately I lack technical knowledge about rump kernels but it was developed to ease development and testing of drivers and various subsystems in NetBSD because you don’t need to reload or run full operating system for that. You can load and run rump kernel with specific modules on userland a use it independently from your running system. Genode used rump kernels to extend their support for filesystems and integrate them as Genode components. You can read more on Genode 14.02 release notes page.