Basicly, there are 2 kinds of users. There are those who have windows and and NTFS partition and want to access it from ROS. (perhaps dual boot ROS and win from the one NTFS partition ambie if that is something ROS can be made to do). These people can use ntfs.sys from MS since they have windows.
Then there are those who dont have windows, dont have an existing NTFS partion and dont have a copy of ntfs.sys. Those people can use whatever other solution we come up with (ReactOS implementation of NTFS, some unix FS like ext/reiser etc or whatever else we come up with).