I'm not exactly sure why, but the error goes away when you click on the DLL, then change the CPU to x86 in Platform Settings, under the tab that has the Unity logo. Maybe that's just a requirement, and if so might be worth an update to the README.
Unhandled Exception: System.Reflection.ReflectionTypeLoadException: The classes in the module cannot be loaded.
at (wrapper managed-to-native) System.Reflection.Assembly:GetTypes (bool)
at System.Reflection.Assembly.GetTypes () [0x00000] in <filename unknown>:0
at Mono.CSharp.RootNamespace.ComputeNamespaces (System.Reflection.Assembly assembly, System.Type extensionType) [0x00000] in <filename unknown>:0
at Mono.CSharp.RootNamespace.ComputeNamespace (Mono.CSharp.CompilerContext ctx, System.Type extensionType) [0x00000] in <filename unknown>:0
at Mono.CSharp.GlobalRootNamespace.ComputeNamespaces (Mono.CSharp.CompilerContext ctx) [0x00000] in <filename unknown>:0
at Mono.CSharp.Driver.LoadReferences () [0x00000] in <filename unknown>:0
at Mono.CSharp.Driver.Compile () [0x00000] in <filename unknown>:0
at Mono.CSharp.Driver.Main (System.String[] args) [0x00000] in <filename unknown>:0
Missing method .ctor in assembly /Users/Keith/Code/astar-unity/Assets/C5.dll, type System.Runtime.Versioning.TargetFrameworkAttribute
The class System.Runtime.Versioning.TargetFrameworkAttribute could not be loaded, used in C5
Can't find custom attr constructor image: /Users/Keith/Code/astar-unity/Assets/C5.dll mtoken: 0x0a0009bf
I'm not exactly sure why, but the error goes away when you click on the DLL, then change the CPU to x86 in Platform Settings, under the tab that has the Unity logo. Maybe that's just a requirement, and if so might be worth an update to the README.