Eclipse 2.1 requires Jaguar (10.2.x), it does not run on earlier versions of MacOS X.

Eclipse is configured to use the 1.3.1 Java VM even if you have Java 1.4.1 installed (however, this does not prevent you from using 1.4.1 and all of its features from within Eclipse). 

Important note about unpacking Eclipse on MacOS X:

Out of the box, Zip files are unzipped using Stuffit Expander. If your version of Stuffit Expander is older than version 7.0 (released 09/19/2002), it does not handle the long filenames that the Eclipse build uses and ends up truncating them, which causes numerous problems.

Furthermore, Mac users use IE 5.2 by default, and the download manager will by default automatically unzip downloads using this mechanism. In addition IE 5.2 does not preserve the long file name of the Eclipse Zip archive.

So before downloading and unpacking Eclipse we recommend to install the free upgrade to Stuffit Expander 7.0 and to use the Safari browser to download Eclipse.