My 6 year old wears Goodnights Pullups as well. From the day he was born he was a very heavy sleeper. Even now, if he falls asleep in his clothes I can completely change him to his jammies and pullup and he does not wake up. I have tried getting him up at night to have him go potty, but he pretty much just sleeps right through it. I used to worry about it but it is just something he is going to have to outgrow. My brother was 10 before he was dry at night on a consistent basis. My parents had tried EVERTHING, rewards, getting him up at night, wearing a special wetness detector that sounded an alarm when he peed. Nothing worked He finally out grew it. If is something he has no control over, you will just have to wait. It sounds like you son might not feel motivated, though. One thing I know that might spark an interest in your son, is how do his friends feel about it? Does he have sleep overs? Does he go on sleep overs? Simple peer pressure might move him to make an effort.
Approximately ten percent of children who are your son's age are still enuretic at night. It makes sense to limit his fluid intake during the couple of hours before bedtime but, apart from that, the situation does not require other interventions.
My daughter is almost 9 and still wears the pull ups as well. She only has a dry night about once a week. She has been through every test there is (which were horrible) and has been on several medications that did not do enough for us to keep her on it. She does not have any liquids after 6. She could care less what her friends think and just happily packs her pull up if she goes to or has sleepovers! The zillions of doctors we have been to just tell us to just relax and she will outgrow it and to not make a big deal about it. So we are finally to the point where we don't. She has to take care of putting the pull up in the appropriate trash can inside and then empty it to the outside can herself. This is not punishment, just responsibility. Good luck!