saserr/xsbt — comment on commit 89659c8cc04e6ce866215d3d2d54d5b13fb2e115
File: main/Resolvers.scala line 41
By saserr:

I think that None means that you couldn't resolve the dependency, and Some(...) means that it is at that location, no matter if you had to download it or not, so other components know where to find that dependency locally. If you check the old code, it has same return semantic as this one.