[eluser]heavenquake[/eluser]
Ah. No problem, no. The CI loader usually returns immediately if the desired library/database/model is already loaded.
However, a best practice is to make sure you don't have multiple load->foo calls scattered all over your code. That way you reduce your debugging overhead when you want to deactivate a specific library -- the other way you risk it is still being loaded somewhere else that you've forgotten all about, and then you need to trawl through all of your code to find it (unless you know som grep tricks).
But it won't break your application if you accidentally load it multiple times, no. CI checks for you.