WordPress itself is licensed under GPL which makes it open source and as such also gives freedom to modify and redistribute. You can red this up on the About page and in the Codex
The Codex is also the place where you can see that people behind WordPress see Plugins as derivative works and as such they also have to be licensed under GPL or a compatible license:
There is some legal grey area regarding what is considered a
derivative work, but we feel strongly that plugins and themes are
derivative work and thus inherit the GPL license.
Implementig any kind of “anit-piracy” functionality would defy the concept of openness, as copying the source code of GPL’d software is not considered piracy but expected behaviour instead. And as the makers of WordPress stand behind the open source idea, I think there won’t be any such mechanisms to be seen in WordPress core any soon.
So if you wan’t to sell your software and have some kind of protection aganinst side channel distribution, you have to add or implement it yourself. An approach for that you can read in Mark Kaplun’s answer here.