The part about not deleting organisms, is a small caveat that I omitted in most of the discussion since it makes the algorithm just a bit harder to understand. To clarify that point, since you asked, the organisms can be popped from the front of the container if we provide a maximum population size. If we do not provide a maximum population size, we do not delete the organisms. Older organisms do however lie dormant due to the non-uniform distribution, thereby providing the same advantage as selection while preserving a greater degree of genetic diversity. If there is anything else that is not clear to you then I am open to any questions you might have. I will help where I can to clarify things.
With regard to the fitness function, I think I agree with you that checking if the offspring matches a password will fall in the category of a fitness function albeit a binary one. I will update my description to include that, thanks.
With regard to if it is useful, I will let it stand or fall on its own merits. If people are going to use it to find bad passwords, then I would say yes it is. It might be pertinent to mention that I am interested in genetic algorithms in general and this is a good practical way of exploring my own theoretical ideas.
Yes, "aaaaaaaaaaaaaaaa" really is a password. Have a look at the rock_you list of passwords and sort them by length. There are some extremely long but silly passwords in there.