Running Different Django Versions But Sharing Authentication
It's possible, but it may be pretty painful to do option #3.
How about Option 4: bite the bullet and upgrade to Django 1.1.1. I did this with a couple of 0.97pre sites and it took less time than I thought it would. The biggest pain was dealing with admin stuff. Instead of going with separate admin.py files, we simply put the Admin classes directly below the Model classes.
I use Mercurial for my DVCS and I just cloned, hacked, merged and it worked. It took about 3-5 hours per site and that included some custom template tag munging.
Brand new to django. We have a legacy django project using django 0.96x that does authentication, ldap, etc., and it's pretty involved so we don't want to rewrite that code.
We want to add a forum solution (off the shelf) but all of the ones I've seen so far require django 1.x 
I'm trying to figure out how to get this working and I've narrowed it down to the following:

Use an old forum solution that works w/django 0.96 (does this exist?)
Try to patch a forum solution to make it "backwards compatible" with 0.96 (possible nightmare)
Use two different djangos: 0.96 and 1.x and (since we're using Apache w/mod_python) have two different Location directives; adjust PYTHONPATH for each appropriately (or use virtualenv, etc.)

But will option #3 even work? I don't know enough about how django.contrib.auth and friends work so if I run two different versions of django will the user stay logged in? I didn't mention trying to patch our 0.96 project to bring it to 1.x but we don't really have the time to do that.
Any suggestions?