This is with CiviCRM 4.6.8 on Joomla 3.4.3.
I successfully installed the Simple Donate Form Extension and it works from within CiviCRM Dashboard, ie, Admin menu settings, CiviContribute menu Test/Live. But, I am not able to make it live on the frontend of the website. I've created a new menu item with the
Menu Item Type selected as
CiviCRM => Contribution Page => Simple Donate Test to no avail. The default CiviCRM form continues to appear. There is little documentation on this other than just set it and forget it.