IIRC, there was a character simply named "Trask", with no first name given. X3 did a lot of that--"lets just give this character this name", even though the movie character and comic character bear no resemblance to one another."
I don't have TLS stand on disk. As I recall, in the movie, the character was only called Trask. I don't remember if the end credits used the name Bolivar at all.