XNJB has the same problem as every precompiled programm. It ships without updatet device IDs which are needed to get mtp working. Mounting is a problem at the moment because it don't get fuse4x to work with mtpfs at Maverick. It always crashes when it hits the symlinks @ Sailfish. But sending and receiving files via mtp-sendfiles etc is possible. But you need to kill ptp everytime you plugin the Jolla phone to your osx.

Some more infos also here:
https://together.jolla.com/question/...-for-mac-os-x/