Reply to The Laws Of Djing

Hello,
I got my S2 today and I have been watching youtube mixes for a while and I was wondering if...
1) if you hear an old song in someones mix, can you make your own with it and still be "chill" (no one gives you crap)

2) Could one use the same songs used in a mix that someone else did?



Thanks,
I believe it would be kind of a cool thread to also have a "Laws of DJing" thread for new people like me, it also just seems like a fun thread to have many people contribute to.

Advise?