Generally agree that most services like this would at a minimum log a matching key w/ alert. I'm not going to audit the code but maybe OP has good intentions.
I made a similar concept, but it wasn't self hosted. I never made the front page though! Congrats. Could you add a video of the experience to GitHub. Without that I wasn't willing to download and give it a go
poker and slots are two very different variants of gambling. Sure, there is plenty of chance/variance in poker but there is an undeniable skill component that is lacking in slots.
I also worked at Scottrade in 2010 and I can assure you that Scottrade wasn't doing arbitrage or marking markets in this manner. I'm dubious of your coworker.