There is no way this is calculated on a 'fair' basis. There are around 3 million apps total between different platforms for mobile. This 1M number must be calculated counting versions of apps as new apps.
Excellent product by the way. Very polished even from early beta.
> our systems have now seen more than 1 million apps integrated with Crashlytics!
If you parse this, "have now seen" != "today has active"