I forgot to mention donations.
As well as using a subscription method to keep a website running, in place of a store, a website can be helped too by donations from it's members, or even non-members.
There is a website with tons of useful freebies by some British artist, and he asks for donations.
What if Mark sent an email to all the 3DCommune members and asked them to consider a subscription system, instead of the store system, and to consider offering donations.
Or is it too late.
I mean if the 3DCommune was really a sharing community, and not just a bunch of sellers and buyers each hording his/her little stake of land so to speak and pretending to be a warm caring community, then surely the members could each cough up 25 dollars to help Mark pay off the debt.
How about if the 3DCommune vendors who are owed money practice some chariity and just write off the amount owed to them to help Mark.

But considering that the free market system is dog eat dog, and that quoting Thatcher, " there is no such thing as society", charity hasn't a chance.

Any predictions when Renderosity will bite the dust?