We had removed the 6.31 update from the download page recently because 6.31 is outdated. However, here are still the links:

http://server.conitec.net/gsa6p/updpro63.exe

http://server.conitec.net/gsa6c/updcom63.exe

http://server.conitec.net/gsa6/updext63.exe

http://server.conitec.net/gsa6/updstd63.exe