Search on Green is a quick-and-dirty hack for Android. The shiny new Voice Search in Android 1.6 (Donut) includes a better voice dialer than the older "Voice Dialer" application. The one problem? There is no way to attach it to a long press of the green button (call/send/answer).
So that's all this application does. If you install it, there will be no new icon to click on, no sign of its presence except that when you long-press the green button, you'll see Voice Search, as it should have been in the first place (the first time, you might need to click "Use by default" and this app). If you don't want it anymore, uninstall it using Settings/Applications/Manage.