Hi Matthew,
Thanks for looking through Calatrava. I would agree, at the moment it hasn't been worked on. However our hope is that we can pick up steam in coming months and get it up and running with latest platform versions and more platforms. We are also constantly looking for user pull requests to help us improve the framework. If you are keen to help contribute please let me know we can chat up individually.
Meanwhile as soon as I have time on my hands, I'll try to fix the broken bits and bring up Calatrava back to running. Meanwhile I would recommend you to look at Xamarin cross platform framework which is C# based and has similar philosophy as that of Calatrava. Although there is licensing cost associated with it and isn't open source. But it helps you create compelling cross platform "native apps".