While the Linux 3.16 kernel is now stable, a few days ago the Reiser4 file-system was finally ported to Linux 3.15.
Edward Shishkin released Reiser4 for the Linux 3.15.1 kernel last weekend. Besides being ported to the kernel interface changes for Linux 3.15, there's also two bug-fixes for the out-of-tree file-system. Most of the Reiser4 activity these days continues to just be porting to new kernel versions and bug-fixing. Edward is down to being one of the only main developers left and there's expected to be no effort to mainline the controversial file-system without the support of a major Linux ISV/IHV.