Can I still download 1.5?

We still make the last Joomla 1.5 version available to subscribers. However, please note that that release will not work with the recent changes to Facebook's API. You can read more about those changes in our Facebook's Graph API v2 blog post .

The Joomla 1.5 version will work for Facebook Applications created before May 1st, 2014 and will continue to work until April 30th, 2015. After that time, all Facebook apps will automatically be updated to Graph API v2. New apps created after May 1st, 2014 are automatically v2 apps, and we can't do anything about that.

I hope that helps answer your questions,
Alex