INSTEAD is described as '– interpreter of simple text adventures for Unix and Windows!'. There are four games similar to INSTEAD for Mac, Windows, Linux and Online / Web-based. The best alternative is Twine, which is both free and Open Source. Other INSTEAD like games are articy:draft (Paid), Spatterlight (Free, Open Source) and AXMA Story Maker (Freemium).
Spatterlight is a native Cocoa application plays most kinds of interactive fiction game files: AGT, Adrift, AdvSys, Alan, Glulx, Hugo, Level 9, Magnetic Scrolls, TADS (text-only), Quill, and Z-code (except v6).