Depends where you are. In Germany you are entitled to a finder's fee by law (in the case of the taxi only if the value is > 50€ and only 2.5% instead of the normal 5%)
If not, I am amazed by your naïveté.
It's moral when you do it because it's obviously the right thing for everyone involved. When there's money involved, that's something else.
This thread hasn't really been about the article for a while. It's been about someone feeling that people that don't reward for good deeds are greedy assholes, which I think sets a bad precedent. If you want to incentivize fine, but let's not confuse that with what the right thing to do is.
How about a moral obligation? Honestly, it sounds like if a taxi driver returns a bag full of cash to the owner, it is perfectlly alright if they just say "Thank you" and walk him to the road. Legally: nothing wrong, morally: being a greedy asshole.
Edit: Fixed truncated second paragraph.
"Taxi drivers and owners must return property they find in a taxicab." - http://www.nyc.gov/html/tlc/html/passenger/sub_lost_prop_inq...
Further: Money doesn't have any owners. Only spenders.
Double standards.
Why not sell it? People sell URLs all the time, and bitbucket is clear written intent from the company that they wanted their source control systems accessible to the public else they would not have provided written notice to the world of their passwords.
Surely the creators of the software are competent software experts who fully understood the implications of making their repository public. Surely, they are not asserting that they were so negligent in the performance of their duties as to not check whether the repository would be made public.
Also, they've made numerous written affirmations that the issue found is not a bug, and would not qualify as part of their bug bounty for security flaws.
They are morons and deserve to be hacked because they are negligent and make affirmations that leaving their source control system passwords on public computers is not a security issue worthy of payment. They deem the risk to be so insignificant as to not even be worth $500.