[plt-scheme] Version incompatibilities in PLaneT packages

DrScheme gave me this error today while I tried to run some code:

Package contract-utils.plt loaded twice with multiple versions:
attempted to load version 1.3 while version 2.0 was already loaded

Why is this an error?  I'd much rather have different versions of the
same planet library be considered wholly different modules, so they
could load together without complaint.  As it stands, I can fix this
problem, but only by editing multiple files, which I may just have to
do again the next time there's an upgrade.  This would be even worse
if other planet modules caused this problem.  If I loaded
"alices-code.plt" and "bobs-code.plt", and Alice used
contract-utils.plt version 1.3 and Bob used contract-utils.plt version
2.0, I'm out of luck.  I cannot fix that bug, yet it seems to me that
code should just run.

Can anyone clarify the situation for me?

--
Carl Eastlund
"Cynical, but technically correct."