Looks clean and simple to use. One suggestion would be to widen your list of emails not allowed to be used - I've taken some to block them from being abused, but at a minimum I'd recommend blocking those listed in RFC 2142[1]
I think it's fantastic. I don't typically hand out a physical business card often. So the recipient would be someone that I would feel would generally find the project exciting and intriguing, and it provides a great conversation piece.
It's simple enough to discuss it briefly and mention that for any security-conscious individuals, they can check out the GitHub that's stated on the card and see the code and still have the same insight if not more than if they had just plugged in the device.
For anyone else, the information they need from a business card is all still nicely stated, in a design that's enticing even without functionality. The production cost is easy to justify with the chance of achieving whatever your goal may be, whether it be securing a job offer or generating new business.
I'm certainly not the most knowledgeable in this at all, but if I'm not mistaken most environments I've worked in have been only the dev instance allows it, while UAT and production won't allow any dirty reads.
I have to agree with you - and has made an excellent transition to whatever is next and built a very strong reputation in the process, and shown enough pride in his product to help let it grow further, even without him at the helm.
I hadn't seen that before, cheers it was an interesting read. I really want to believe that my mind still can't dismiss acknowledging that there is always a possibility they have undisclosed back doors, it's just a matter of what it takes for them to disclose it. As more time goes by my thoughts on that possibility lower though, as more people are exposed to the code as a potential outsider/doesn't agree with the practice.
[1] https://www.rfc-editor.org/rfc/rfc2142