This company is incredibly rude. If you accept a job offer somewhere else and let them know, be expecting a hostile and unprofessional email back.
Here’s the thing, SwiftKick: Developers are rarely interviewing for a single position. Instead of treating potential future employees terribly just because they accepted another offer, build a relationship with them and maybe they’ll come work for you in the future.
If this is how you treat people who aren’t your employees, I can’t imagine what it’s like to work for you.