OnX 1.7 for Mac was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. This free Mac application was originally produced by Realmac Games. The software is included in Games. Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe.
From the developer:
OnX is a simple game of Tic-Tac-Toe with an interface look similar to Apple's OSX Aqua design.
You may want to check out more software for Mac, such as WinOnX, which might be similar to OnX.