The 4.5 version of ArcExplorer for Mac is available as a free download on our website. The application is included in Education Tools. The most popular version of the tool is 4.5. The actual developer of this free Mac application is ESRI.
From the developer:
ArcExplorer —Java Edition for Education is a new version of ArcExplorer built primarily to support the Macintosh OS X platform, in addition to Windows. With ArcExplorer —Java Edition for Education, users can view and query local data as well as ArcIMS services from the Geography Network or other hosted sites.
This freely downloadable software comes with several prepackaged project files and sample data to get users started.
You may want to check out more software for Mac, such as AEJEE, which might be similar to ArcExplorer.