Short answer, yes, the legs never rest.
Long answer is that this is the Darebee way. If you look through the programs, the rest is already incorporated as an active rest, where the body faces off physical activity that isn't as taxing as the regular workouts. It should be known that you must listen to your body, and if it demands a rest, you should take it, no matter what. Challenges are special because, most of them, don't have rest at all. They are supposed to be a challenge to take on a daily basis, hence the name "challenge," and they are programmed in such a way that you can do a challenge on a monthly basis. They work perfectly as an addon to your regular training, because, as you can see, the majority of the challenges are microworkouts that aren't really as taxing as the regular workouts.
Just take it slowly, and rest if you need to. It is ideal that you do it on a daily basis, but no one is holding you at gun-point to make it daily, so it is fine to skip a day if you need to. Life happens, anyway.
If you're restarting to your training, it's a good idea to check out the
Foundation program as a way to get back into your training. Plus, Foundation will also give you a general idea of what workouts we do around here. Welcome!