Github user joewitt commented on the issue:
https://github.com/apache/nifi/pull/2184
We cannot take a document/source/item from some place unless it has a
clear/compatible license for it. If there isn't one at all or isn't one that
is favorable to our needs as an ASF project we cannot use it. So either we use
all originally created source or we cite it. Does that make sense?---
