Rename List, Map, and Set to something like Vector, Dictionary, and Bag. Rename corresponding interfaces Vec, Dict, Bag and StaticImports functions mutableVec, mutableDict, mutableBag.
Provide a separate version of Paguro for Kotlin. Maybe all unit tests would be written in Kotlin?
Provide a pure Kotlin version with the above changes.
For now, if you're using Kotlin, you want the 3.1 version. Java-only, stick with 3.0. The 4.0 version looks like it will be a rewrite in Kotlin. I'm closing this because no more input is necessary.
Thoughts: