From this page, you can download various older GEMPACK command-line programs, dating from Release 11.0 [October 2011].
For example, GEMPACK Release 12 and later may be unable to read very old solution [SL4] files, created by GEMPACK 8 [2005] and earlier. You could use the older SLTOHT program, contained in the archive below, to convert the old-format SL4 files to a modern HAR file.
The programs are contained in a 7Z archive -- you may need the 7-Zip program to unpack it.
Download utes2011.7z