Hi,
Sorry for the issue. First of all: Most prior releases of our packages are available on our downloads page.
From there navigate to: Download other archive formats
Scroll down to where you see the first Kunena 1.6 listing. By default only the latest package is shown. Only need to click on Kunena 1.6 it self (first column on joomlacode.org) and it will show you all current and prior packages of Kunena 1.6
Now to the problem at hand: This is another one of these Joomla menu issues. Unfortunately Joomla is rather particular how it wants menus set up. It has to do with the way Joomla uses itemids for menu items.
In your case Joomla uses the menu-item alias for SEO.
If you get into those redirect loop situations, it is most likely due to two separate menu-items (can be in multiple menus) using the same alias.
If you want a very simple menu link to the forum, we suggest you remove any manually created ones and use the create Menu button in the Kunena backend to have it automatically setup.
Hope this helps!