I didn't read it as ZenPayroll trying to redefine what "hacker" means. Rather, they are simply stating what "hacker" typically describes in the context of a job

I didn't read it as ZenPayroll trying to redefine what "hacker" means. Rather, they are simply stating what "hacker" typically describes in the context of a job board. In my experience, their described usage is pretty common, especially among hiring posts for startup jobs.