I’ve poked around the Tiobe Programming Community Index from time to time, but had never noticed that Inform is among the languages that they track. As of August 2011, Inform is solidly in the middle of the pack. While they don’t publish the precise ranking for languages ranked lower than 50, they do list Inform as falling somewhere in the range 51-100 (out of roughly 150 languages tracked). That puts it in some pretty good company (including Smalltalk, which was the first programming language I ever studied).
TIOBE added a bunch of new search engines to their ranking algorithms. Inform is one of the big beneficiaries, not only getting back on the list but actually cracking the top 50.
So to continue the natural-language metaphor, Inform’s now about as widespread as Swahili.
(Okay, this is a slightly sneaky comparison, because the ranking there is about native speakers, whereas Swahili’s fame comes largely from being a lingua franca. But it doesn’t sound as cool to say ‘as widespread as Uzbek or Sindhi’.)