> "Opps, shit did I link with something that requires I release the source".

that can't happen. all that can happen is "sorry, you can't use this unless your code is under a compatible license". and if that is the case usualy
you say you are sorry, drop using that library/whatever and you are fine. worst case: you are forced to take your software off the market till the situation
is fixed (wouldn't affect your windows or mac os X version unless you use the same library there too), and in theory someone could sue you for compensation
of damages. But all the cases I followed that never happened.

don't let the fud get to you. some people claim if you combine A with B then A is suddenly under the same license as B. that is not true. but: you are not
allowed to combine A and B unless their licenses are compatible. and if you make a mistake usually it is good enought to stop combining A and B or find
some other compromise.

without investing too much time you can figure out which combinations are ok. don't worry too much, take come basic care and you will be fine.