import Darwin.ncurses in Xcode 7 Beta 1 no longer automatically links ncurses for you, has to be done manually. This does not seem to be intended behaviour. Apple has changed some stuff related to frameworks in Xcode 7 that has caused a known issue, which seems to be the culprit [1]. They have introduced .tbd files, "'text-based stub libraries', that provide a much more compact version of the stub libraries for use in the SDK, and help to significantly reduce its download size." This is the format that libncurses is listed as now, not as a .dylib.
One workaround is to manually add libncurses.dylib to the build phases setting in Xcode (see 5baea59).
[1] https://forums.developer.apple.com/message/8609#8609