I have a ‘copyright-related’ question. If I get some free assets from the Unity Asset Store, can I use them like they’re Creative Commons 0 license (aka Public Domain)? That would mean I can use them freely even for commercial purposes without mentioning the author etc.
Yes, you can use any assets you acquire from the asset store freely in your commercial projects without crediting the author. But that is not the same as saying they are in the public domain. You are not allowed, for example, to distribute or reproduce the Assets in any form (other than embedded as part of your game), and in using the assets you are bound by the terms of the EULA.
Legally, the owner has granted you a non-exclusive license to use the Asset in your project - they retain all copyright and other intellectual property rights over the asset.