There are several discussions here in the developers corner section of the forum regarding scoreboards, some of them even mentioning groups.
Try going to the main dev corner index page, and searching for the word "scoreboard".
Ive no idea if any are Murder specific, but any discussion of scoreboard would likely have similar GUI/derma code.
As i've mentioned in a few of the other scoreboard discussions, we have a nice command called "
GetUserGroup" that would return the group the player is in.