If you work with IBM Mainframes (z/OS, z/VM) on a Mac, you’ve probably noticed a glaring issue: every halfway-decent TN3270 terminal client costs money. Sometimes a lot of money. We’re talking $50–$100+ for software that essentially emulates a 1970s text terminal. One popular commercial option even charges a recurring subscription just to let you type on a green screen. That felt absurd to me. The free alternatives out there usually fall into three categories: They require Java (slow, resource-heavy, and clunky on macOS). They run inside X11 (no thanks). They are abandonware that breaks on every macOS release. So, I decided to build my own from scratch. Introducing DX3270 After a weekend of intense frustration and diving deep into ancient IBM GA23-0059 architecture manuals, I released DX3270 (hosted under the X3270 repo). It is a completely free, MIT-licensed, native macOS TN3270/TN3270E terminal emulator. Check out the repository here: GitHub I wanted something that actually feels like it belongs on a Mac.…