I agree with duotive and Parallelus
Strictly speaking, regular licenses don’t cover usage on multiple sites, whether or not they are part of a multisite install. In practice, I’ve had the same experience with the multilingual issue - it seems fair to consider that a single usage if, like Parallelus said, the content is the same on each site.
Honestly doubt you’ll get an “official” answer (the only one that could possibly be given is the strictest adherence to the license I think), but if you want could try contacting support.