I must admit I thought that domains that go into official registry Redemption Grace Period and on into Pending Delete were fair game for everyone too.
I thought that names could only be auctioned off before they went into the "delete cycle".
Godaddy names can only go to the tdnam.com auction up until around 30 days or so after renewal date, as far as I know. If no one makes a bid on them at tdnam.com, they can be acquired by the godaddy.com backorder system (guaranteed or not guaranteed, depending on when the backorder was placed), or if there is no backorder placed "in time", then they can be acquired by "anyone".