Below is the beginning part of its README file:
PSTOTGIF Copyright (C) 1993, Wolfgang Glunz, Siemens AG, email@example.com
pstotgif allows to convert Postscript files to a simple vector graphic format, that can be edited with tgif. Ask archie on where to find tgif. pstotgif works by redefining the two basic painting operators of Postscript, stroke and show. Others like fill or image are not supported. After redefining these operators, the Postscript file that needs to be converted is processed by GhostScript (gs). So you need to have Ghostscript in order to use this program.