Three of the six Pythons, Eric Idle and Michael Palin, (both 69), and Terry Jones (70) are due to give evidence in the five-day legal action at London's High Court.
Mr Forstater is suing all three and the two other surviving Pythons, John Cleese and Terry Gilliam who are abroad and not expected to give evidence, for an increased share of the Spamalot millions. The sixth member of the team, Graham Chapman, died in 1989.
A judge has been told it was the "worldwide commercial success" of Spamalot that appeared to have led in 2005 to a cut in the size of his share of the profits from Grail spin-off merchandising Mr Forstater enjoyed for almost 30 years.
Tom Weisselberg, appearing for Mr Forstater, argued that financially the film producer was entitled under an agreement made in 1974 to equal treatment with the Pythons. But the Pythons said they could not recollect any agreement.
Mr Weisselberg told Mr Justice Norris: "The outrage expressed by a number of Pythons in their witness statements as to the suggestion that Mr Forstater was to be treated as the seventh Python is, with respect to them, misguided.
"There is no suggestion that Mr Forstater would be writing jokes, but what was being agreed was that Mr Forstater would share equally with them in the profit in the work they were together putting in to create the film."
The court heard the film producer was made bankrupt in June but he is now involved in an independent voluntary arrangement (IVA) to deal with his debts.
If Mr Forstater wins his overall claim, it is unofficially estimated that it could eventually earn him a £1m figure.
The hearing continues.