While I can't respond to what is required, legally, in other countries, here in the US, Jenoptic can do nothing about third parties reverse engineering their equipment to work with these cameras.
That is specifically allowed. Even the DMCA allows this for the purpose of integrating one product with another. The DMCA only applies to DRM'd products, which is not even the case here.
If Phase 1 is serious about moving their backs to this camera system (assuming it does sell in large enough numbers, and enough purchasers are unhappy with the supplied backs), there are no legal problems here for them to be concerned about. This goes for mechanical, as well as electronic, and software, integration.
As an aside, My thoughts as to the shortcomings of this camera relates to the fact that it is an entirely new system. One year is a very short time to go from concept to working product with systems at this level of complexity. I would suspect that a generation II product, perhaps in another year, or less, will solve most of the problems seen here today. From my own experience as a designer, and manufacturer, I can see that this product is not "finished".