ABAP stack or Java Stack? Is ABAP stack Mandatory?

Hi guys - Can you tell me where I can find information in regards to Java stack versus ABAP stack. I am looking to see if FS-CM and FS-CD modules can be installed only on Java system or ABAP engine is mandatory? if FS-CD and FS-CM availabile on either the ABAP stack, Java stack or require both? Both would have a sizing impact right?

Regards

K