I've really only seen two confirmed aliases for Mobusta in UT3- Mobusta and HATR3D.  He technically has several others but they were only used for a map or two.  He is known as mo` at x22cheats.com and on x22's IRC channel.  He's still active on x22's forum as a moderator but I've seen nothing that convinces me that he still plays UT3.  So it's likely people are making false claims that someone is Mobusta.  He's still cheating but I think he gave up UT3 a long time ago.

UT99 and UT2k4 dwarf UT3 in the amount of cheats and SDKs that are out there.  Personally I don't think there's as many people cheating in UT3 as a lot of people are claiming.  If there is then there's a large underground network that managed to keep their cheats secret for years.  I heard CARNAGE got x22 from someone passing it to him but after reading the chat log I think that's a bunch of horseshit.