I think SimpleWiki should be a bit more documented especially for passing the callbacks I was a it confused because in the actual doc, it is written "array(objectref,'methodname') " I searched in the simplewiki code how callbacks were fired; I wanted to call functions that were not in objects, I think your documentation should refer to the call_user_func manual page.
I also had to search the muster code for symlinks as I didn't know how to handle it in my function, think you should also add something like :
"Your function should modify the linkparts->internalselector property with the relative link to the concerned resource. Asked resource is read from the same variable."
in the Muster_SimpleWiki::register_symlink_handler documentation.