I moonlight as a ski instructor, but I usually ski during the daylight hours.
I'm not going to put words in ICSFM(AM)'s mouth, but when I think about the OP, I'm thinking along what is right vs wrong. Giving free tips while in uniform is good. Teaching friends and family while out of uniform is fine. Teaching 9-5 coworkers for free (even people I've known for years) while in or out of uniform???? Hmmmm, that one's pretty sketchy. If I'm social with them normally and consider them a friend, yeah, fine. But if it's some joe from down the hall? No. If it's some hot Betty? hmmmm, maybe
I think, with any of those situations, you could easily get away with it, because you knew the person from outside of skiing for a while and could claim it to be whatever you want (personal guilt aside).
I think the bad freelancing is when you solicit random, unknown people to take lessons with you at a negotiated price, and bypass the ski area's lesson desk. I think that the instructor soliciting people for work is key to this. If someone comes to me, I think the door is a little more open to interpretation.
Here's an interesting thought. As an instructor, I know and understand these rules. Even the unwritten ones. but lets say I move to Utah and don't pursue a job as an instructor, but the people I work with know I'm a long time instructor and someone decides they want to pay me to give them a lesson????? Or what if I'm out on vacation for a month and someone I run into and am making a couple of runs with says they want to pay me for a lesson? They come at me with something like "I've taken lessons here before, and I never liked any of the instructors, will you teach me, even though you aren't working as an instructor? I'll pay you $XX for a few hours of your time."? As someone who loves to teach, but isn't currently employed as an instructor, how would you handle that? To be 100% honest, I'd be really tempted to take them up on it. Then again, I may also decide to approach the SSD and get their opinion and maybe ask if they would let me work as a temp for free lift tickets and/or for pay, and have the person sign up through the ski school. Of course, if they said no, then what? Again, it seems to be coming down to who is soliciting whom for the lesson.
Now for a stickier situation. What if I move to CO or UT, don't get a job as a ski instructor, but put up signs soliciting myself for ski instruction in my place of work? It feels dirtier, doesn't it? But maybe I can't gain employment as an instructor due to lack of availability or something, and I only do this a few days a season? What if I tried to get a job teaching, but they turned me down because I can't commit to enough hours, yet someone I work with wants a lesson from me, and doesn't want a lesson from the random instructors that always get assigned to them at the ski area? Doesn't feel quite as dirty any more, but it's all very grey.