Actually, brushless AC and DC are pretty much interchangeable. The term came about because PM servomotors were traditionally DC, so the first brushless servo motors were dubbed BLDC even though the current wave form was AC. I don't know who makes the motor.
So the motor used by Pentair, according to them and this thread, is a permanent magnet synchronous motor, or PMSM. Evidently another name used for this type of motor is PM brushless AC and/or PM brushless DC. Do you know whether the Pentair IntelliFlo is using the AC or DC flavor of this motor?
The term PMSM is actually not commonly used. Although it is technically correct, it is not an industry-standard term like BLDC. BL servo motors are generally not made in NEMA sizes larger than size 42. Although many motor companies will make custom versions to be NEMA 56 compatible, the standard versions are oftentimes proprietary (or follow a european mounting norm, of which I'm not that familiar).
I did a quick search last night on the Internet, but could not find any manufactuers of PMSM in a NEMA 56 frame (most pool motors are NEMA 56C or 56J frames or NEMA 48 frames). In fact, I really couldn't find any manufacturers of PMSM at all, although it appears that some hybrid or electric cars are using PMSM motors (redundant phrase, I know) to drive the wheels. PMSM motors appear to have been traditionally used in servo motor applications in the past, but evidently they are beginning to become more widely applied.
Re: Aspen Motion Technologies. I don't really know much about them, but it's very interesting to note that they are located in Radford, VA. Radford is not a very large town, but is also happens to be the home of Kollmorgen Motion Technologies. Kollmorgen, which was bought out by Danaher about 10 years ago, had two servo motor manufacturing plants there (Industrial Drives and Inland Motors). Aspen Motion Technologies just happens to be right down the road (Rock Road, to be exact) from Industrial Drives. I suspect that Aspen was started by some ex-Kollmorgen engineers who didn't like working for Danaher. If that's the case, there is some serious motor building knowledge in that town.