The question of "onsite or not" is surprisingly complicated.
To the casual fan, "onsite" means "has all the perks of staying 'at Disney'". Only resorts that are owned and operated by Disney meet this critiera. You can tell if a resort is wholly owned by Disney if (and only if) it is named "Disney's <something or other>".
There are hotels that are on Disney-owned land, but are not fully "onsite" by virtue of not being wholly owned by Disney. They include Shades of Green, Swan, Dolphin, and the seven DTD hotels. They provide various degrees of access to "onsite" perks, but none of them provide all of those perks.
Bonnet Creek is an oddity, because it is landlocked by Disney-owned land on three sides, and I-4 on the fourth. You can only get to/from it by "entering the gates", and there is Disney signage that points to it, so it seems like it is on Disney-owned land, but it technically isn't. As with some of the DTD resorts (which are
on Disney-owned land), Bonnet Creek offers none of the standard "onsite" perks. However, it's closer to many other Disney destinations than some of Disney's own resorts. For example, folks staying at OKW or SSR will often find themselves going
past Bonnet Creek on the way to or from the parks.
Depending on who you ask, Bonnet Creek's location is anything from a minor annoyance to a major concern for Disney and, especially, DVC. They have gone so far as to put a 3D billboard advertsing DVC smack-dab across from the driveway into Bonnet Creek, so that anyone leaving the BC site can be reminded that they don't really belong.
As for exchanging in: Wyndham controls all deposits from Bonnet Creek (as well as any other all-point resorts.) Up until about three months ago, there hadn't been a whiff of Bonnet Creek being deposited into RCI in years. Then, a few very-off-season units showed up. More recently, a handful of primetime units got deposited. I personally saw a 1BR during President's Week for '09. So, it's possible, but you have to be
very flexible about when you are going, and you'll need a pretty good trader to see the larger units.