SETL was developed by Jack Schwartz. Many years later Gary Levin developed ISETL (Interactive SETL) for Unix, DOS, and Macintosh at Clarkson University. ISETLW (ISETL for Windows) was developed by John Kirchmeyer at Mount Union College with help from research assistant Jamie Wylie and partial support from a Tomsich Science Research Grant during the summer of 1995. Much is owed to Ed Dubinsky, whose idea it was to use SETL for teaching Mathematics. He also influenced Gary to create ISETL and encouraged John to create ISETLW. Other early contributors included Nancy Baxter and Don Muench.
ISETLW is a true Windows program. It is fully mouse and clipboard enabled, has Windows-style menus and push buttons, uses typical dialog boxes for opening and saving files (including changing drives and directories), knows how to print to Windows printers, supports cut, copy, paste, and single-level undo, can deprompt highlighted text for pretty-printing (but you don't have to deprompt as you sometimes need to with ISETL for Mac), allows timing of code executions, and has no artificial memory barrier related to DOS limitations.
ISETL is available at the Mathematical Archives and ISETLW is available on this server. Both may be copied and distributed by anyone. See Downloading ISETL and Downloading ISETLW and read the readme files.