Traditionally, the interrupt pin was connected to a pull-up and driven by a number of open-collector (TTL) sources in a "wired-or" (active low) configuration because that is how you implemented a common interrupt line on a computer bus.
So it was indeed, "active-low". "Active high" is simply not used. Since you should not be wiring for example, switches to pull high, this should never be a problem, but note of course, what retrolefty says.