TMFS - Apple's Time Machine fuse read only file system.
sparsebundlefs - FUSE filesystem for reading macOS sparse-bundle disk images.
mergerfs - Union filesystem geared towards simplifying storage and management of files across numerous commodity storage devices.
gefs - Good enough file system.
libfsapfs - Library to access the Apple File System (APFS).
proper-lockfile - Inter-process and inter-machine lockfile utility that works on a local or network file system.
Sanoid - Policy-driven snapshot management tool for ZFS filesystems. When combined with the Linux KVM hypervisor, you can use it to make your systems functionally immortal.