Originally posted by victormeldrew There is absolutely, definitely, 100% no clear answer, because there is no clear law in place that I know of, in any jurisdiction.
It depends on where you live. In Canada, it's quite clear: you need a release to publish any picture with a recognizable person. The only exceptions being editorial use, in the sense of "newsworthy", or if the person is just an incidental character on the picture and not its subject. It doesn't matter if you make money or not with the picture. The difference between public and private place is only related to the right to take a picture. Obviously, you can't publish a picture if you did't have the right to take it in the first place. Or, in other words, there's a difference between the right to take a picture and the right to publish it... Or as, stated in a decision of the Supreme Court of Canada on the matter:
Since the right to one’s image is included in the right to respect for one’s private life, it is axiomatic that every person possesses a protected right to his or her image. This right arises when the subject is recognizable. There is, thus, an infringement of the person’s right to his or her image, and therefore fault, as soon as the image is published without consent and enables the person to be identified.
In the specific case described by the OP, it would be clear: a release from the dancers would be needed to put the pictures on his photography website assuming the dancers are recognizable, even if it could have been perfectly legal to take the pictures since it was a public event in a public place.