I think it's the collector in me. This is a game that is something special that only comes along once in a blue moon (Nethack and DCSS are my other all-time favourites) and I'd love to possess a physical museum of its evolution.
Anyway, back to your point, bandwidth wouldn't be a big issue, though certainly it would take some more work to put together and make it available / maintain it. That said, as long as you're a registered owner (I can see you are--but I mean anyone else, too), I'd be happy to offer a download of all previous releases on an individual basis to those who request it. I can't imagine the demand would be huge at this point.
I probably couldn't offer to do this indefinitely, because it does take time (= money), but in the short-term while demand is low I could manage.
That's a kind offer, and I'd like to take you up on it. As I said, I've got Alphas 6 and 4b, so I'd like to get hold of the others. For my part, a) I promise to d/l subsequent releases in a timely fashion so I won't miss any again and I won't bother you again, and b) I'll buy another licence as a token of my thanks.