Unless I'm mistaken the hub is a part of DC (Direct Connect) network. ie: a network separate from G1 or G2, etc. There are multitudes of DC hubs, some are private and only accessible via an invitation (and possibly a password/ID though I might be mistaken; it depends upon how private and strict the specific hub is.) In some cases, the particular hub represents a specific style of music or other topic; a common interest.

As I recall using DC last decade, there are occasional invites to groups through the BOT chat channels. But they still need to be approved by one of the group/hub leaders. Some groups/hubs (or it might be all) are set to a maximum number of members and are inaccessible when already full. I don't know how many changes have occurred since last decade.

What's good about DC? Album and other topic downloads. Easier to find specific styles of files. Perhaps a little less so in the public hub arena. Private hubs are a good way of privately sharing between such members.

I'm guessing all you need to do is retain your settings as they are now for Shareaza to re-connect to DC. Sorry I can't be more helpful. The Shareaza forums might be able to help further.