This tool is dedicated to site collection administrators. They can create SharePoint groups based on any audience.
MOSS audiences can be built dynamically using audience rules based on metadata criteria like for instance (Any employee belonging to the departmenet HR will be put to the HR audience etc...)
You can easily create audiences in MOSS using the central administration UI. You don't have as much flexibility regarding SharePoint groups. So, the idea of this tool is to create/maintain SharePoint groups FROM MOSS audiences.
You'll be able to create either a "one shot" group, either a group and its corresponding timer job that will be responsible for maintaining the group membership based on the associated audience.
These details are provided for information only. No information here is legal advice and should not be used as such.