"What is Vince?"

Vince is an application that allows the user to choose which applications are set as helpers for internet protocols (i.e. which application will be chosen to handle which URL)

Basically it replicates the "protocol helpers" preferences pane in IE.

"For God's sake why? It's already there in IE"

URL handling is integral to OS X - therefore the ability to change which applications handle these protocols is also integral to OS X. Currently the only way to do this is through IE.

Therefore in order to configure something that is integral to the Mac OS you have to use *a web browser* that is built by Microsoft - If that doesn't seem wrong to you then you've already given your soul to Bill Gates.