BlenderKit only has 2 available licenses, and these are quite simple. Everything you download is available for commercial use. Both allow you to sell higher-level-derivative works, but royalty free license doesn't allow to re-sell 3D models even if modified.
This license protects the work in the way that it allows commercial use without mentioning the author, but doesn't allow for re-sale of the asset in the same form (eg. a 3D model sold as a 3D model or part of assetpack or game level on a marketplace).
CC0 - No Rights Reserved
CC0 enablescreators and owners of copyright- or database-protected content to waive those interests in their works and thereby place them as completely as possible in the public domain, so that others may freely build upon, enhance and reuse the works for any purposes without restriction under copyright or database law.
In contrast to CC’s licenses that allow copyright holders to choose from a range of permissions while retaining their copyright, CC0 empowers yet another choice altogether – the choice to opt out of copyright and database protection, and the exclusive rights automatically granted to creators – the “no rights reserved” alternative to our licenses.