Disney (DVD specifically) is being intentionally vague. What they are trying to do is stop renting altogether, but they cannot for two reasons: it is specifically allowed under the terms of the contracts and DVD is the largest renter of points.
In the beginning, before social media exploded, members really had to rely on word-of-mouth to find renters/customers for their points. Then, brokers came along and made it easier to match owners with renters. Once people realized how easy it was to advertise and post reservations for rent and reach thousands of potential customers, commercial renting was born. Most owners did not dive in head first and buy up thousands of points with the sole purpose of making hundreds of reservations and posting them for sale...but some did...and those are the people Disney is going after. They have zero intention of taking a vacation with their points and they have no "personal" use for the reservations as they are solely for income (commercial) purposes. Make no mistake, Disney knows who these players are. Now that members have to acknowledge that the reservations are for personal use, any members who are using their membership commercially (and remember, Disney surely already has these memberships flagged) must answer this question honestly. If they don't check the box, they are basically admitting that they are using their points for commercial use. If they do check it, and Disney performs an audit of their account, there may be consequences.
The confusion and concern is with the "everyday" member. What does one define as "personal" use? If it is open to interpretation on a discussion board, certainly it is intentionally vague on Disney's end as well. If a member owns 400 points and regularly travels using 200 points per year and then rents out the other 200 points to cover their dues, would that constitute "personal use"? Some would argue yes and some would say no. They are certainly not making an income or a business from the rentals and half of their membership IS being used for personal travel. Disney is breaking it down by the reservation and using the word "personal" to make it more confusing. No, the owner does not have to be travelling for it to be a "personal" reservation. No, the owner does not have to know the people travelling for it to be a "personal" reservation. Yes, you can receive compensation for the reservation and it is still a "personal" reservation. The rental companies (specifically DVC Rental Store) have made statements saying that they actively work with their members and they monitor who they are receiving reservations from so they watch for repeat listings. If they see too many pre-booked rentals or points for rent from the same membership/owner, they are pro-active in order to protect potential renters from having their reservations cancelled. I would say that booking a rental reservation from a broker is still a very safe way to book a DVC reservation and DVC rentals are not going away any time soon.
As an owner of a small number of points, I do appreciate DVC's efforts to curtail commercial renting. There is no need to have weeks of pre-booked reservations listed for rent 9-11 months in advance. Renting is a nice way to recoup costs and help others enjoy DVC without the cost/commitment. Pre-booked/Speculative reservations made in the 7-11 month windows are just money-grabs in my opinion. I do not have any issue with people renting out to confirmed customers in the home resort window, but they should have their dates confirmed. Home resort owners should not have to compete with "ghosts" for their reservations.