If two people running vanitygen 1abcdefg What is the chance that both of the person will get the same public key & private key?

I hope that the answer is less than 0.0000001. But for this vanigygen need to use random algorithm (not simple while(true){ i++; test()}).

My question is: Usually when I create wallet, using http://bitaddress.org I need to Move your mouse around to add some extra randomness, but vanitgygen do not do this method.

By inspecting the code of vanitygen in GitHub I see that they use random functions. Can I trust it? Is it really random? How it can be secure? Is it use the machine time or what?