AppleShare 4.1 uses a more recent version of the Apple Shared Library Manager (ASLM) than what is installed by the Internet Router.
Apple Internet Router 3.0.1 installs Shared Library Manager 1.0. While AppleShare 4.1 needs Shared Library Manager 1.1.2 or higher.
The issue can be resolved by performing a custom install of AppleShare 4.1 and selecting Shared Library Manager.