The point is to allow module developers to sell, maintain and update custom modules, and to allow other DW partners to buy these.
The market could go as wide as to also contain designs like Themeforest does for wordpress.
Support and updating is done by the module developer, sales, financial- and file transactions are done by Dynamicweb. Plus perhaps some modest quality control. I imagine something like different levels of commitment, based on user reviews and number of quality modules produced.
First custom module from a developer gets held back for review, then released. If it gets good user ratings, the second one doesn't need a review and the developer moves from grade C to grade B if this module is also well rated.
In this way, a lot of content and possibilities will be developed, and still only require a low level of commitment from DW. To the benefit of all.
Like with Wordpress, I seen the possibility for an entire niche of module developers to evolve.