Who must have the license for publishing games - developer or publisher? For example, I buy the license, then I develop a game and then I sell my game to the publisher - should the publisher buy his own license? Or it’s enought that I have one? Sorry if it’s stupid question…
All the features a pro license contains, are only for the developping and publishing phases. Once your project is published, the published application itself doesn’t depend on a license 
As you probably sell a standalone application or a webplayer build to your publisher, he doesn’t need a license.
However if you sell him the Unity project itself, he will need one. (if you used pro features, else he doesn’t)