The runtime should revert to the US English language module and continue loading. If you install OpenDCL Studio, it sets a registry key to specify the language so that it doesn't look for a nonexistent language module. If you only installed the OpenDCL Runtime, you can set this registry key manually. Just create a new string key named "Language" in HKLM\Software\OpenDCL and set its value to "ENU". OpenDCL Runtime will then look for the resource DLL in the ENU subdirectory.
I will investigate how this situation can be improved in Alpha 4.