I'm not related to craftpix but I had the same question, so here is the license:
https://craftpix.net/file-licenses/
2. FREEBIE PRODUCTS
2.1 CAPABILITIES
- 2.1.1 You are permitted to use the resources in any number of personal and commercial projects for yourself or a client.
- 2.1.2 You can modify the resources according to your requirements and include them into works such as game projects, elements for websites, applications, printed materials and others;
- 2.1.3 You can sell and distribute games with our assets.
No attribution or link back to this site is required, however any credit will be highly appreciated.
2.2 FORBIDDEN
- 2.2.1 You can NOT resell the art source files (PNG, JPG, EPS, Adobe Illustrator, etc) or slightly modified version of the art. You can not redistribute the art or modified version of the art in a manner that would make some or all of the art files useable to another end user via the app. For example, an app that uses the art as part of the play of the game is fine. An app that allows the user to save or export a modified version of the artwork itself is not fine.