The letter evidence in and of itself is not that big a thing, the main point around it is that BBRV submitted the letter knowing it was false, and even if he did not know, he purposely kept the court in the dark about it when it was proven to be false.
This is why they went on about the osts on the forums so much.
It shows hard indisputeable fact that BBRV purposely submitted false evidence at worst, used it as fact to further his case in full knowledge he was misleading the court.
Amiga Inc's reply has ben solely about showing that BBRV was never acting "in good faith" and that he always had ulterior motives in attempting to gain more than was intended by the contract.