TIBCO BusinessEvents 5.6.0 onwards, it is not mandatory to install TIBCO ActiveSpaces along with TIBCO BusinessEvents in TIBCO BusinessEvents Application Docker Image.
If your application is In-Memory, you can just specify TIBCO BusinessEvents Installer as input to build_app_image script. If your application uses Cache or is connecting to external AS cache cluster, you need to copy TIBCO ActiveSpaces *.jar and *.so files (or *.dll depending on your container OS) into the same folder where you have placed your CDD and EAR files. You do not need complete TIBCO ActiveSpaces Installer. This helps reduce TIBCO BusinessEvents Application's Docker Image size.
In general the image generation process and scripts are much more streamlined in BE 5.6.0 as documented here :
https://docs.tibco.com/pub/businessevents-enterprise/5.6.0/doc/pdf/TIB_businessevents-enterprise_5.6_cloud_deployment_guide.pdf