George Tsoai, 25, and Raymond Mabelebele, 26, were found guilty of the murder of 24-year-old Nkosinathi Mhlongo.
The third accused, Tibane Serumole, 24, escaped a life sentence and was sentenced to 15 years in jail - with the option of a R15 000 fine.
The two students who got life attacked Mhlongo and his friends after they complained about their smoking on the bus.
When sentencing them the magistrate, Doctor Nkuna, told them they could appeal if they were not satisfied that they had been properly punished for their crime.
Mhlongo was murdered in 2008 while returning from a trip to Pretoria organised by various students movements to hand over a memorandum to the minister of education.
Nkuna told them they should have behaved like students.
"If you had behaved like students the court was going to treat you like students, but you behaved like criminals, so the court will treat like that."
The sentence was delayed in June after the defence applied for the probation officer to provide a report on the accused.
The report by three social workers said the three accused had not indicated any remorse over their actions.
Nkuna told the three while sentencing them that a university was a place to produce leaders - not ruthless, barbaric individuals.
State advocate Sam Mamabolo said: "This court wants to send a clear massage that this type of barbaric behaviour is not accepted by society."