I added it and get C:\apps\ctsapi which is the root directory of the application - not the bin folder, but the directory that contains the bin.
This is apparently correct behavior in asp.net as per http://stackoverflow.com/questions/8669833/why-appdomain-currentdomain-basedirectory-not-contains-bin-in-asp-net-app
I've also had a bit of a play and found that the place where it fails. The line "Dim NewDLL As New MfgControl.AdvancedHMI.Drivers.CIPforPCCC" in EthernetIPforSLCMicroCom.vb is where the exception occurs. I assume this is where the closed-source DLL comes into play?
This is being addresses and should work in the next version.