TeXnicle 2.3.1 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. The actual developer of this free software for Mac is bobsoft.
The common filenames for the program's installer are texnicle.app.2.2.9.zip or texnicle.app.beta29.zip etc. The unique ID for this application's bundle is com.bobsoft.TeXnicle. The latest version of the program can be installed on Mac OS X 10.6.8 or later. We recommend checking the downloaded files with any free antivirus. The most popular versions among TeXnicle for Mac users are 2.2 and 2.0. The program belongs to Education Tools.
From the developer:
TeXnicle is a LaTeX editor and project organiser for OS X with a feature-rich interface to help you manage your LaTeX projects. Features project organization tree tabbed editor with syntax highlighting, code folding, code completion, and more built-in comprehensive symbol library code snippet library file templates full project search bookmarks dynamic document outline configurable typesetting engine
You may want to check out more software for Mac, such as Celestia, PCalc or GeoGebra, which might be similar to TeXnicle.