In many cases, double-clicking an .indd file's icon will cause the wrong application to launch.
InDesignProxy fixes this by working as a 'stand-in' for InDesign and InCopy. You can drag/drop any .indd file onto InDesignProxy, and InDesignProxy will analyze the dropped document and then forward it to the appropriate version of InDesign or InCopy.
You can hold the Option (a.k.a. Alt) key while drag/dropping a document onto InDesignProxy. This will bring up a dialog for selecting an alternate version of InDesign or InCopy - e.g. if you drag/drop a CS2 version, this dialog would allow you to enforce it to be opened in CS3, even if you have CS2 installed.
What's new in this version:
Fixes an issue where InDesignProxy would change the 'last modified' date of any InDesign documents it 'touched', which throws a spanner in the works for people whose workflow depends on accurate 'last modified' dates.