I won 4 free airplane vouchers and a voucher for a free night in a hotel from Blue Green Resorts. They called and want me to go to a seminar to pick up the tickets. Will they say I have to buy a timeshare to get the tickets? If so, isn’t that illegal?

Free vacation? right… In this lifetime, there’s hardly anything that’s free… it’s like a small publicity thing, so you might receive the vacation (but don’t be surprised if you don’t get it…)
As for having to buy something, doubt it… if you don’t want it, don’t get it, but if it’s in their rules that you must buy something to get the "free vacation," then that’s what you’ll have to do…
They can not condition your gift. Read the fine print just in case and be ready for a pulling teeth sales presentation.