EDIT: Problem solved. See here for a how-to on setting up for DLL compiling in MonoDevelop using UnityScript. I've puzzled my way through getting MD to compile DLLs for UnityScript, but when I actually use those DLLs in Unity I keep getting errors which I believe are because MonoDevelop is compiling for the .Net 4.0 framework even though I have set the target framework to 2.0. I have duplicated exactly all the settings in Unity's own Assembly-UnityScript.unityproj and included the exact same references, but when I check my compiled DLLs with ILSpy, it tells me the runtime is 4.0 whereas the default Unity project DLLs compiled to Library/ScriptAssemblies all show as runtime 2.0 in ILSpy. Expanding the references in ILSpy, mine show mscorlib 22.214.171.124, and Unity's show 126.96.36.199. I can't figure out how to force MonoDevelop to compile to the .Net 2.0 framework. Even stranger, Unity's Assembly-UnityScript.unityproj says the target framework is .Net 3.5, but the final compiled DLLs show runtime 2.0 in ILSpy. Some kind of behind the scenes magic must be going on when Unity compiles its projects. By the way, the error is: Code (csharp): MissingMethodException: Method not found: 'System.Type.op_Equality`; Every site I've come across says this is because System.Type.op_Equality was added in .Net 4.0 and is not supported in earlier versions like Unity uses.