it's used for mesh networks (but can also be used for other applications) - some freifunk communities in germany use it and there is ongoing development to port the most popular mesh firmware called gluon to use babel as it's a layer3 mesh and gluon is using a layer2 mesh (using B.A.T.M.A.N) - layer3 scales better because with more nodes you have a noisy switch on layer2.

Fascinating stuff - if you want to learn more about babel here is a technical talk from the developer: https://www.battlemesh.org/BattleMeshV8/Agenda?action=Attach...