1) Short
2) Diverse shot requirements, recoveries, and/or ways to play a hole
3) A fair amount of quirky features and/or unique holes
4) Not an easy pushover scoring-wise
Kalen's definition is pretty good I think. You could probably add in rough and ready as from my take from how the term "sporty" was used in old periodicals it often was used as a euphemism for courses covering ground that still had to be tamed ! I'd also maybe add hazards in no. 3 above. Of course what we now consider quirky such as walls, quarries, roads etc would just have been considered hazards back in the day.
North Berwick pre 1895 redesign with it's quarries, walls, beaches, woods, gas works building etc was definitely considered sporty and not necessarily in a bad way. As to whether sporty was bad or good I think depended on the eye of the beholder as even the better players could still enjoy sporty courses even if those types of courses tended to be a leveller.
These days some of our nine holers such as Strathtay, St Medan and Beith would definitely be considered sporty.
Niall