"...I would think they couldn't, somehow sounds wrong. Am I right?" If it walks like a duck & quacks like a duck...
Actually, I was replying tongue-in-cheek. Since you already knew the answer - but asked anyway; I assumed you were looking for validation - which is why I dredged up all the other questions I've seen asked on these boards...think I covered all the bases for any similar situations.
At least once a month someone will post a similar thread wherein either they want to use a Deluxe pool while staying elsewhere or want to invite guests to join them in their fun. Had a conversation w/a CM wherin they relayed the problems they have, especially during the summer months with this situation. He indicated the problem is especially rife w/locals who pay for 1 room and "load it up", so to speak.
At some resorts the problem (yes, it is pool-hopping!) is so prevalent (Y & BC) that you must, @ all times have resort ID to use the pool. During the high-season the BW also stations a CM to monitor the pool @ all times (too many folks parking @ BW, going into Epcot & taking a quick dip in the pool before they head out).
Bottom line is one of the reasons deluxe resort categories charge more for their rooms is the amenities (including the pool) that they offer. Which is why guests not staying @ the resort are prohibited from using the pool facilities. All are welcome to visit & use most of the other amenities (some have extra fees - exercise facilities, etc.)
BTW, one of the current "percs" offered to DVC members staying as guests is the ability to pool hop to selected resorts if we check in @ front desk & inquire as to capacity issues. This does exclude AK & Y/BC & certain busy times of the year. So, even that gimmie is subject to their discretion if their facilities are full.
Although these boards are a wealth of information, despite what other have posted, to get the definitive answer - call the Resort Desk directly and ask to speak to the Mgr. or Asst.; you'll get all your questions correctly answered.
As for appearing unfriendly, I'll beg to differ...I'm trying to save your extended family the embarassment of being approached by a CM poolside & being asked to leave...as well as hoping to be able to utilize a lounge chair poolside on my next trip.
As I indicated in my OP "...no flaming intended, just good natured common sense...enjoy the magic".
If it isn't real busy and your family wants to join you, WDW propbably isn't going to care. As much as some of the people on these boards want to believe they know it all, they don't. Just be sure to get it OKed with the front desk. WDW is the final word, not this board. And for the record, I do not pool hop. In fact we rarely go swimming when we are at Disney. We would rather be having fun in the parks. I can go swimming without having to drive a 1000 miles. 
For the record, I wasn't trying to commit a sin. This is why I asked to prevent doing any wrong doing. You could have answered without being so unfriendly. 
. I just felt really bad for the OP 
. I should have kept my keyboard shut 
!
