Can you safely can homemade caramel/butterscotch syrup?
I haven't seen a butterscotch canned recipe but the ball blue book has a couple syrup canning recipes that look fantastic. If you do any canning you should have this book. The recipes are invaluable.

These recipes use the hot water bath technique. The extremely high sugar content would be enough to keep it preserved. Modifying one to be butterscotch should be straight forward. 

I wouldn't try any experiments that reduce the sugar content because then we're getting into the risk-of-horrible-paralyzing-death area of canning.