I'm offering a 7-day, no-questions-asked refund. Feel free to try it the way you like, and if you don't like it, you will receive a refund in less than 24 hours. I'm happy to assist if you have any other questions.
I've never seen a successful Show HN that required a credit card signup, just FYI. You can offer a free code in your Show HN text that HNers can use, if you want to limit the reach of a free offer.
That's a great gesture and I appreciate it, but it's still a lot more friction than just a free trial. Is the concern with a free trial that people will pirate it?