The Captains I fly with use the seatbelt sign like the airlines but no one really seems to care, just like the airlines. I'm not a big fan of using it since most clients that fly charter or corporate are smart enough to figure it out that its too bumpy to stand up. If I know it's going to be bad I'll go back ahead of time and give them a little heads up. It's just annoying to have that ding go on and off if people are trying to sleep.

I'm also curious how corporate flight departments use the cabin signs