Interesting discussion, though I think the terminology is really in the way. What most agreements resemble most is a car lease, where you make a down payment and pay a regular fee (whether monthly or annually). The problem when applying this model to the software industry, is that you cannot just go to a different leasing company and get the same product.

Regarding Microsoft not following this model, I beg to differ. Enterprise software from Microsoft enatils a maintenance agreement, whether you pay for it separately of include it in the up-front licensing fee. I hate to think what a mess we would all be in if we did not get any maintenance support from Microsoft, whose code seems holier than the Pope. Unfortunately we seem stuck with it forever.

Perhaps there should be a new paradigm, but what it should look like is a very thorny issue, since whole corporate financial models are based on the status quo.