I promised to shut up, but since you ask:
Let’s say you find a nice unlicensed preset off the net, and make a hit song with it. Later it turns out that the preset was an illegally redistributed sample from vendor X, who sues you. That’s your headache.
However, what if said preset is included on the Zynthian, and a Zynthian user then goes to make a million dollar hit song using this preset? And then the vendor starts suing?
It may seem unlikely, but I wont call it far-fetched because that’d be belittling the device and its users. Just that it’s a situation you don’t want to put yourself or the users in, no matter what.
Quoting zynthian.org homepage:
You can use it for live performing, studio production or as a tool for sound exploration.
Zynthian is a community-driven project and it’s 100% open source. Free software on Open hardware. Completely configurable and fully hackable! Free as in Freedom.
That’s a pretty strong statement that there are no proprietary materials included, but maintaining that requires a continuous effort from everybody involved. It’s not a matter of personal beliefs.
And now I’ll really shut up 