"The kernel is 2.6.18-based with the addition of Samsung's Robust FAT File System (RFS),..."
Open access to RFS source trees would make porting forward to current kernel releases possible. This mutual benefit to Samsung and the community is the whole point of open source development. As it stands Samsung must bare the cost of reworking RFS and porting it forward off the past end of life 2.6.18 kernel.
Developing new projects around 2.6.18 is going to requires a lot of out of tree maintenance. However I am not surprised Samsung developed custom FAT for flash, we nearly did the same.