The whole point of our releasing appjet-in-a-jar is that if we go bankrupt, you can still host your app yourself.
We'll definitely charge money at some point, but right now we're focused on improving the platform for developers. Also, we have a spiffy virtualization engine for hosting apps that allows us to do it at negligible cost. So it costs us next to nothing to host our current load of 2,249 apps and ~3M combined monthly pageviews.
It seems like they could have a straightforward, profitable business model: for example, you would be able to get started for free, and once you start using more of their resources you start paying a reasonable monthly fee. the more you use, the more you pay. That way they could offer way more than 50 MB of space, and present themselves as a serious platform rather than as a toy for amateurs.