The Distribution application will work with System 7.0 or greater.  It only takes up 96k on your disk.  

RAM requirements:
Up to 100 destinations (folders): 190k
Add an additional 100k for each 120 additional destinations (folders)  (i.e.  Set Distributions memory requirement to 600k for 800 mailboxes or folders).  

A Distribution Applet will also work with system 7.0 or greater.  The RAM requirment is a meek 25k.  You will need to increase the amount of RAM if you are distributing to more than 200 folders (This is as far as we have tested).  The disk space requirements for the applet depend on the number of distibution destinations (folders).  For a single destination the applet will take up approximately 12k with an increase of approximately 1k per destination.  On my BBS, one  distribution applet takes up 102k for 160 destinations.