sans FTL communications
Well, some of us read your post, some didn't.
I actually thought of the NASA protocol right away, but apparently I wasn't alone.
Actual inter-planetary internet would likely be near to impossible, to say nothing of extra-solar... I think you nailed it with the title: it would pretty much have to be built like freenet, distributed storage, at least for the off-planet stuff, refreshed periodically, more often for the more popular, less for the fringe stuff.
Direct communications would likely be limited to emails, or thier video counterparts. I can't see real-time conversations working too well between say, mars and pluto, even at closest approach. Might be used for stuff that needs an answer NOW.