Not sure about official DCNR policies or what trailhead signage might say, but from a practical standpoint many PA SF ATV trails are open to ATV users only seasonally, and in the 'off' season are used by (at minimum) hunters, hikers, and cross-country skiiers. That said, I see Whiskey Springs touts both summer and winter trails, so not sure that happens much at this particular area. Might be best to just to email the forest district. 