Seldom
10
If you can extract the files from the NSIS installer, and they include IMG files, an Overlay Map IMG, and a TDB file. You can use MapSetToolKit to INSTALL (button on bottom right near center) the maps in your MapSource/BaseCamp.
Note that MSTK only performs a simple registry edit to do this, and it will work with mkgmap compiled maps. The START button requires cgpsmapper and only works with cgpsmapper compiled maps.