Basically there is a powerful Joomla component available which would let you link these Open Source Application with each other.
JFusion proves that Joomla is the future of CMS softwares. Which other CMS software can act as a portal and integrate your users across multiple different platforms? None! Now you have full control over all of your web applications using JFusion.

Download JFusion

Currently supported softwares are;
1. vBulletin 3.8.0
2. phpBB 3.0.x
3. MyBB 1.4
4. SMF 1.1.8
5. Magento
6. Moodle
7. Gallery2
8. dokuwiki
9. Elgg
10. Oscommerce 2.x, 3.x, XT, Zen, Max, SEO

A number of modules are provided with the JFusion package such as;
1. Login Module
2. Latest Activity Module
3. User Activity Module
4. Who is Online Module