Boondocking website

Yes, I'm very familiar with it and YES it is legit. However you should understand that what it offers is basically "driveway surfing". You can spend the night (or several nights, depending on the host) in someone's driveway or on their land. These are generally not out-in-the-wilds boondocking spots and often-times the driveway won't be more than a concrete pad to park on right outside their house. However if that's what you're looking for it'll fit the bill.

I have several RV buddies who've used it extensively in their travels.