Learning Language Through Rumors/Eavesdropping

Does listening to the spoken part of rumors help with language learning, or does a language need to be spoken by a PC/NPC?

Listening to vNPCs speak will also help with the language, yep. Wherever there's an interaction with a spoken language in proper quote tags, that can impact your language learning. Currently there's a bit of a lack in the sense that rooms can't .... speak, really, so the vNPC 'object' is actually something concrete that secretly teleports around wherever it needs to and changes its profiles. It's a really sloppy programming solution and I've been debating how to fix this with myself for a while now and I think my brain's finally starting to settle on a decent idea... we'll see! #everntually

But, long story short, the answer to your question is yes.