We don't like/understand or want to enter the market for selling to end users (low cost, high volume, high earache, low clue). We sell the underlying JavaScript diagramming library at higher cost in lower volume and I find the more developers pay, the more polite they are to deal with.
This is simply the main example application that ships with the library. We just deploy it on Google App Engine, it does all the availability and scalability for us. Because it's pretty much entirely client-side, we pay trivial costs for serving a little static bandwidth and it gives us free marketing for the library.
So, it will stay fully featured for free and I don't want to pollute it with ads and you'll be seeing a large number of new features added through this year. We're also considering open sourcing the diagramly part (not the core mxGraph, you'll be able to use that hosted Google Maps style) so people can throw up their own custom diagramly sites.
Are you hoping to be bought? Are you just trying to help people out? Are you already rich?
As I said, it's awesome, and I'm going to use it. But I just want to understand the motivation!