First things first, this set of rankings is based on data from GitHub and StackOverflow. Read the post for the details on how this data was collected.
There are plenty of other ways to assess the popularity of programming languages, but this seems a reasonable approach.
It’s notable that Swift has tied Objective-C. As the post says:
Finally, the apprentice is now the master. Technically, this isn’t entirely accurate, as Swift merely tied the language it effectively replaced – Objective C – rather than passing it. Still, it’s difficult to view this run as anything but a changing of the guard.
Pass this along to your dev friends.
The problem with the metric they’re using is that if a language falls into disuse, it’s score won’t go down. It seems to be just the number of Stack Overflow posts graphed against the number of GitHub projects. So popular languages can crawl over the backs of a stagnant language, but the stagnant language will never slip downwards on its perch.
Sorry for not being able to parse this from the linked post, but does this ranking include apps that are still being actively used, but might not still be actively discussed as new projects by developers?