It's the 星, つ星 of Infinity- I have an actual quote somewhere about it but I can't find it right now. Both Anthony Keidis and John Frusciante (damaged due to drug use) have it as a tattoo: link
Actually, Anthony 発言しました that the symbol had no particular meaning. He was told to make a logo for promotional purposes. It began as a simple アイコン that he drew on a piece of paper. Anthony has a tattoo of this symbol on his wrist.
