In order to load the eFile to the simulator you only need the .cod files. To compile you do need jars.
Here is where you can get them:
http://www.dynoplex.com/files/eFile_API_Installer.exe - the API with docs and cods.
http://www.dynoplex.com/files/eFileAPI.2.138.021.zip - most recent jars.
Of course you also need the cods of eFile itself to run it - download it from
www.dynoplex.com/downloads.shtml.
Hope this helps.