There are a number of reviews stating that this trail is not open to the public - is it or isn't it? If it IS open to the public (and not solely available to the surrounding neighborhoods) where can one securely park without issue?

Definitely open to public. Can park at H C Nesbit park, trail entrance is down a gravel road from the traffic circle at the park. There is a parking lot at the park. There are multiple entrances in Millbridge, don't park on the street, use the parking lot at the pool and community house. Check in at the Millbridge Community House if you have any concerns about parking there

It is open to the public. There is a smaller trail nearby that is for the neighborhood only. In Indian Land there is a park and Waxhaw, if you look at the map you can see, park at either one.