[plt-scheme] guibuilder and drscheme versioning

when i install guibuilder.plt
(http://www.cs.utah.edu/plt/develop/guibuilder.plt ,
http://download.plt-scheme.org/scheme/plt-clean-cvs/collects/guibuilder/ ,
and http://download.plt-scheme.org/scheme/plt-clean-cvs/collects/guibuilder/
), i get a error saying "cannot install; archive is for a older version of 
PLT scheme".  However it dosn't mention what version it was written for. So
I've got 2 questions.  #1, what version of drscheme do i need to install to
be able to run guibuilder? and how do i generally figure out what version
something is written for?

You can see a cool picture of guibuilder in action at
http://www.cs.utah.edu/~mflatt/tmp/guibuilder.jpg

Corey

(please responpd to the list, since this address isn't my real address, 
it's just for posting to lists)