Hi asdfgh, welcome to MobileRead.
If you don't register, at least with Adobe, you won't be able to download and read Adobe epub files with DRM. Other than that, and getting updates wirelessly, you can skip it.
Seems to me I saw the instructions for that on the enTourage support site: http://entourageedge.com/support/
If you don't find it there, and you still want to skip registration, let us know and someone who knows more than I do will (hopefully!) answer you.