DoubleTake 2.7.3 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 software lies within Design & Photo Tools, more precisely Viewers & Editors. 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. The actual developer of this software for Mac is Echo One.
From the developer:
DoubleTake is the "nano" of stitching software. Drag-and-drop your images onto or into DoubleTake, arrange them, and check the overlaps. When you are done - save and perhaps copy and paste the result to iPhoto.
You may want to check out more Mac applications, such as Sequential, JetPhoto Studio or BannerZest Pro, which might be related to DoubleTake.