yeah actually the driver told me that the ticket doesnt guarantee a seat
so i.e. with the bus you have if they had oversold you would have gotten bumped to the next seat on that route..even if it is MANY hrs later!
they do not guarantee seating!
also non refundable means you will not get your money back, but it can be credited towards another ticket need be.

sourse: i traveled from burlington to boston last month on a non refundanble ticket. at the transfer pt , bc my bus was late, i miss the conection and panicked that i couldnt get to boston. the station explained i have a ticket to boston - just wont get my money back.. and told me to wait for the next bus or come back another day!