You do need something like UGCS. The post processor for Cut2D is there so that Cut2D can generate the appropriate G-code for the X-carve. Once generated you have to have a program to actually send the G-code to the X-carve.
You can use UGCS, Chilipepper, or various other programs that perform that function.
I am looking into UGCS because it looks like it will do the job and is not very much complicated.
Downloaded the UGCS master from Github - it says I need to install it by clicking on the .Jar file, problem is I cannot see any jar file there.
Then downloaded a V1.0.9 version (has only 4 files) - seems like its working but I do not have the Arduino and Gshield boards yet - so I guess I will have to get them first