So a bit of history. Back in the early days of MASON development, we put together a social networks package due to an internal request. It's called 'socialnets' and is part of the contrib packages right now. That package isn't used much and hasn't been tested much. But it's pretty well done i think, and with some polish maybe we should roll it into the rest of MASON.
'socialnets' has a lot of analysis facilities but doesn't have any visualization: it builds on MASON's network package and so its social networks may be visualized using MASON's network facility. Which is moderately primitive.
Maciej Latek, here at GMU, wanted to use JUNG instead, and decided to write some code which bridged the two a while back. That's the Jung package you see on the MASON website, and it's the 'jung' package in the contrib directory. It's not been updated in quite some time, and so no doubt is suffering from bitrot as MASON gets updated. Also Jung isn't known for its speed.
Hooking MASON up with other people's libraries often entails a bit of hassle because these libraries often aren't particularly well designed, and are rarely separable, serializable, or self-contained. It's annoying: they don't think about interoperability with other toolkits. For example, we had to bug the JTS folks to get them to add serialization so GeoMASON would be serializable like a proper MASON toolkit. JUNG is typical of this unfortunately. It doesn't help that JUNG hasn't been updated for three years.
So anyway with some tweaking you should be able to get the JUNG toolkit working again with MASON -- we haven't deviated that much. Also Richard, if you'd like to add some contributions to the JUNG contrib directory, or indeed take it over, let me know. And last, try the socialnets package. It'd be nice to have people banging on it and finding bugs or making improvements -- it's a nice little package I thought.