Cricket has it right. The stickiness is a sure sign of scale insects. Ferns do not ooze sticky sap on their own.
Treating ferns for pests is problematic because many fern species are damaged by pesticides and even soap and alcohol sprays.
If it is a Boston fern, you can give it a crew cut, then spray with soap and alcohol and there is a reasonable chance that the new growth will come in pest-free. If it is a maidenhair fern, then it is best to discard it.
I once had a beautiful and very large staghorn fern that developed scale. I was never able to eliminate it, but I managed to keep it in check for many years. Sometimes that is the best you can do.
Good luck with yours!
the fern might have been damaged. or has insects of some sort or be deseased.the sap might be comeing out of it as it is trying to heal its self. or to use as a deterarnt toward the insects.i would let it go with out water till the soil drys up some this should stop the sap from driping.when it stops then start watering it again.hope this helps your friend in gardening DIGGER 