http://www.brainstormsw.com/weblog/archives/221
It explains namesakes and runs through this graphical representation of a BrainStorm model:
In brief, all blobs are entries. Identically coloured ones are namesakes, they are chained together with hyperlinks making navigation easy. The dashed lines lead to shared descendants. Any namesake appears to own the same descendants. If they are altered, the changes are shared by all namesakes.