This isn't too surprising. There is a tremendous amount of work to do and too few people who can understand it enough and are willing to do it. In fact I can only count 2 people who were mostly involved and maybe a handful of others who were on the fringe. It's all been fantastic work, but unlike PSO I just don't think there's even that much demand for a PSU private server software.
For those of you who found this, there is an offline expansion project which is bringing a lot of the online content to offline mode here
. This has a good chance of being the only PSU project in existence.