Diversity was one of my first apps, and it has been discontinued. In its place, I now offer Taxon, an even better tool for quickly entering, analyzing, and exporting your ecological data.
Diversity is no longer available on the App Store, and it will no longer be updated. If you have purchased Diversity, it may still run under macOS, but I cannot say for how long that will be true.
Migrating your data from Diversity is easy: go to File ... Export Group of Collections and Diversity will create a comma-delimited file with all of your data. This file can be easily read into R. It can also be imported easily into Taxon by choosing File ... Import Census Matrix.