I think the CRM Dynamics Marketplace is a good idea, there hasn’t been much information about it. Then slowly but surely the information is appearing and things are becoming clear.
but finally Microsoft made a blog with the FAQ’s, it contains details about costs and the testing (and where) you need to do to get your app listed in the Marketplace
I then found this excellent video which runs through the 5 steps you need to go through to get your apps listed
I would add that some of these steps won’t be taken by developers because listing the company involves putting in lots of data and you will need to describe your company