Is CDH required for Oryx 2 ?
According to matrix summary, it seems required (along with Kafka parcel). But, the top of the page not indicates CDH (but it lists Hadoop 2.7.0 and Kafka 0.10.2...).
Can I just use Hadoop and Kafka (not Cloudera Kafka parcel) ?
It's not required. Nothing about uses anything that would be particular to CDH. It uses APIs in a pretty simple way.
Given limited time, I only test on CDH, and make the versions fit the combinations of component versions that appear in CDH releases.
However if you got similar versions of these components to work together independently, I don't know of any reason it wouldn't work.
You're most likely to run into version problems with Kafka.