Ran it on phoc as well - it doesn’t tell the whole truth since the repository did not preserve rootston’s history, but at least some trend can be noted:
I guess hacking it to consider the first commit to be in a separate cohort could show us more 
[edit]
…or we can just use months as cohorts 
There was still some Purism’s code in rootston before forking though, so that’s not counted.