It was written in E, but is often played in D by people who find the original key difficult.  Dave Richardson (from Wallsend-On-Tyne originally) wrote it on mandolin, and on that instrument the two keys have quite a different character.  "Calliope House" was the house of piper and arts administrator George Balderose in Pittsburgh.  The tune turned up as part of the Waterboys "Fisherman's Blues", and was in the original production of Michael Flatley's "Lord of the Dance"; when they realised that it wasn't traditional (or Irish, come to that), it was removed, presumably so that they didn't have to pay any more royalties.

Malcolm