Rockbox WPS parsing code has changed quite a bit since 2006, there is no reason to believe that WPS should work out-of-the-box.
That WPS is in the graveyard because it was not released with a permissive license, which means modifications of it can not be distributed.
To fix it (for personal use) one would very much need to take it apart, see what it is attempting to do, and then basically rebuild it from scratch, unfortunately.