I think the law get more complex when we're talking about designated private communities.
It IS funny how hyper-concerned we get over the legalities of it all when it's Catholics and a private relgious community we're talking about..and not some liberal, selective, "artist community" subsidized with city funds for attracting the coveted "creative people."
Anyways, my guess is this is all probably moot because the website for the development does not mention any restrictions on who can live there.
How often do the Amish sell their land? I bet for the most part it is passed down from generation to generation via inheritance.
...or so I can invade one of those designated "artist-only" condos where their candidates are selected by a board.
Occupation is not a protected class, religion is.
Here in Philadelphia, we have self-selecting Catholic communities. Start with terrible public schools, add in a law requiring city residence of city workers, put in a dash of a forceful tradition of Catholic schooling, and spice with intelligent home owners who understand the concept of vetting buyers before agreeing to bids and want to sell their homes to people like themselves to keep their neighborhood nice. End result? Most of the middle-class white neighborhoods in the city are 65-90% Catholic (the variable is generally the Jewish and German Lutheran element of the population - a rather constant 10-15% are other Protestants), even while the region as a whole is only 40% Catholic. This outcome is simple. Most non-Catholics don't want to send their kids to Catholic schools, and the only other viable option financially for most outside a few Lutheran and Jewish schools, are the public schools, which are just abysmal.
The same result is also present in some of the inner-ring suburbs where the public school system has deteriorated, resulting in a residual white middle-class population that is 65%+ Catholic. Generally, once a neighborhood reaches that sort of monolithic level, it drives out diversity as it gains a reputation as a place for the predominant group of people, and other people simply refuse to move to it.