Battle Network and Starforce are in a separate timeline from the main series. My theory is that the only change is which profession Tadashi Hikari (Dr. Light) chose, but that's not offically stated fact. Battle Network is present day and Starforce is that world in the 2200s. Not connected to the robots timeline at all.
Or do you mean how is he megaman? When Geo Stellar and Omega fuse, the fusion is called Megaman.