There are some gambling sites online that give free money (approximately 0.5 $) to each registered account. Is it ethical to program a bot to create accounts for warranted profit ?
Supposing that the scheme works, then it's reasonable to equate it with any abuse of shopkeepers. Is it ethical to take all the cheese in the cheese sample bin at the grocery store? Is it ethical to fill the store with actors pretending to shop but with no intent to buy anything? Is it ethical to write false messages on the customer service comments cards?
The fact that the Internet enables anonymous human interaction gives us the feeling that we're not responsible for our actions, but that's not really true. Whatever we do anonymously has exactly the same direct effects as actions done under ordinary human identification.
Is it ethical to do something wrong, provided that you can get away with it?
Ethical and legal can and do diverge from each other unfortunately.
It is unethical on the implication that each registered account is intended for human gambling. Implementing a bot to automatically register accounts is against the intended purpose and incentive. The issue of lying on the name and email fields for these fake accounts is unethical.
I recall a very similar instance below where a man was arrested for creating several stock trading accounts for the automatic deposit and was charged. Additionally, it would be considered fraud to generate multiple accounts with fake information for the premise of collecting monetary deposits.
Largent's script allegedly used fake names, addresses and Social Security numbers for the brokerage accounts. https://www.wired.com/2008/05/man-allegedly-b/
Based on the above, do not risk it.
Kant is a good reference. Can this universalize?
If a lot of people did this, it would most likely drive the site into bankruptcy. So you are taking advantage of them as a mere means, and not considering a fair outcome for all parties involved.
That changes if you find gambling itself unethical, you think they shouldn't be in business to begin with, and that is your purpose. But then you should not be depending upon others' malfeasance for your income, because if you universalize that, everyone gets their comeuppance, and you are broke. So you should do it, but not keep the money.