It's already known elastic made elastic search code base proprietary. So if anyone who uses their distribution without proprietary license will likely be sued.

It's very difficult in a mixed proprietary and open source code to figure out which one and which one is not proprietary. Also given the terms and conditions and license text is written broadly, it can be changed at will.

I will not side with sun guard or elastic here. Use Vespa or solr or some other software if one wants to use open source. Don't touch ELK with encumbered license.