It seems the MapViewer software supports opening files in Golden Software Interchange Format (*.gsi) and as such it should be possible to save the data in MapViewer's own .gsm document format. As fat as we know, no other 3rd party software is capable of this conversion.
Convert Golden Software Interchange Format to MapViewer document file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert gsi to gsm on Windows
A mapping and spatial analysis tool
Convert from gsi file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.