It sounds like your co-worker does not have the Apprenda SDK installed. Make sure they install the same version of the SDK that you are using. The SDK installers for supported versions can be found here: http://docs.apprenda.com/downloads
Another way to solve this is to create a lib directory in your project and copy the Apprenda SDK files there and check them in as part of your source and fix the references. This way they will always be there no matter who you give the code to and will also prevent you from having to install the Apprenda SDK on the build server.