The jfs source code is available correct? So if you wanted to you could make your own variant of jfs, call it myjfs? If such a filesystem existed how could you reverse engineer the parameters in order to read it without the original source. This is a forensics question so please don't get the wrong idea just thinking out loud.
Ps What makes a file system unique, the nitty gritty please. Or a link to where I can find this information.