BMPR File Specification is not available
There is no documented file format specification on Balsamiq Mockups website
Go to site and find a well documented specification of the new file format called BMPR
Go to site and find an archived version of the BMML file specification
ADD documentation that explains BMPR, along with what controls look like and what properties they have.
Why does this matter
Users who are familiar with integrating/extending Balsamiq Mockups into their apps are forced to resort to the old version of Balsamiq Mockups because there is not a publicly available spec for the new format.
I have started working on an unofficial BMPR spec to help others get used to the new format. I understand developers are probably already familiar with JSON, but non-developers may experience syntax overload like I did (since I wasn’t used to JSON). I have a file on Github that I plan to improve upon in the coming weeks. Since the old BMML spec was publicly available, I assume that BMPR will be too, that is why I am using Github.
I have also copied and pasted the portion of the BMML Spec from the pdf you have provided on your website. I plan to improve upon that as well, for the users who don’t want to switch to BMPR right away. I will use Markdown syntax to organize it and do it justice.
I also found a site called Read the Docs which allows users who have documentation on Github to manage it and allow their users to download the documentation in multiple formats. I would love to see Balsamiq Mockups be on this site, just because the documentation is easy to navigate and it would help those developers mentioned earlier with conveying the specifics of the JSON programming language and how it relates to BMPR.