I personally would think the best way would be to get permission from Martin, have the base package on the CD, have Go Play In Space on there if you can get permission from the author to do so, and have links to the addons.
I agree with Tommy, most developers would probably allow you to include their addons, but I know (from what I've read) that Dan won't allow you to put OrbiterSound in there. That's not a bad thing, though, again, as Tommy said, it means that if no-one's re-distributing it, he can be sure that people are getting the newest version. Heh, maybe the addon developers should go down the well-worn SVN path... Back to the topic.
Remember, though, that at this confrence you can easily have a couple of machines running Orbiter, show them it with all it's awesome addon glory, give them a CD with the base installation, Go Play In Space, and a list of reccomended addons, perhaps also an explanation of why you can't legaly give out the addons yourself. I'm sure that, after seeing the awesomeness of Orbiter, people will be more than happy to download OrbiterSound, the DGIV, UMMU, The XRs, ASMO, IMFD, and so on themselves. I sure did.
And just one side note to Donamy: Well, they can take you to court.