Where did you find documentation that it's not possible to have more than 6 apps running. The long press of hte home menu simply shows you the LAST 6 apps that were run, not the ONLY 6 apps that are running. If you use a task manager you'll see that many more processes are running at the same time.
The OS manages this space based by cutting off an application or moving to background/idle state if some other processess is needed (or requested by the user) and memory is getting lower.
The OS manages this space based by cutting off an application or moving to background/idle state if some other processess is needed (or requested by the user) and memory is getting lower.