If that's really what you want then you need to write code to put on the dongle which communicates with your ek board via bluetooth and sends/receives data in and out the usb serial port (/dev/cu.). Then you talk to the dongle from your mac over serial.
Sort of hard to know why you'd want to do that. That means writing an app for your ek, and app for the dongle which translates between serial port and BTLE and an app for OSX which talks to the serial port. Is that really what you want?
If you just want to talk BTLE to the EK why can't you use the OSX BTLE libraries.
Because my mac's built-in bluetooth cannot find the broadcasting from ek, although iphone/android/windows can see the same broadcasting. The mac is brand new with bluetooth 4.3.
well it will be a lot easier to figure out why you're having trouble getting OSX to work with the EK than it will be to build a custom application on the dongle and a custom app on the mac to work around it.
If you were thinking that you could just plug the dongle in and have it work like an external bluetooth adaptor, you can't, it doesn't work like that. And as far as I remember, even if you did have a 3rd party external BTLE adaptor, OSX doesn't support them, it only supports using BTLE over the internal BTLE chipset.
You'd probably be better off heading to the apple dev forums, or the apple bluetooth dev list if that's the bit you're having trouble with.
