EXPGUI is a graphical interface for the GSAS software, allowing structural refinement using the Reitveld technique.
EXPGUI/GSAS can be downloaded in binary form from http://www.ncnr.nist.gov/programs/crystallography/software/downloads.html
You need to install tcl/tk and also blt all of which can be found in debian package repositories. (Or whatever for your system!)
apt-get tk8.4 blt
tcl/tk is the scripting language used to write EXPGUI.
failing to install blt will result in the error “Error — Unable to load the BLT package; cannot run liveplot”.