DVC has a corporate membership with II. When you trade DVC points via II, you do so under the corporate membership. Only those who own a timeshare affiliated with II, which allows for individual membership in II, may receive access to other II member benefits, such as the bonus vacations.
There are a few websites that offer rental bonus weeks to the general public. They generally cost more than the bonus weeks offered to members of RCI or II. They are also usually more limited to shorter notice and/or offseason. Sorry.