I have already read the DevAssets guideline but I’m not sure if I can modify the assets that I downloaded from the websites.
Can I modify the assets AND use the assets commercially for my project?
So what I take from reading the assets guidelines is that so long as you don’t download as resell them as your own work, you can pretty much do what you want with them.
What I would probably do if I were in your shoes would be… to revise them as I wanted, but then credit with a small line somewhere in the deep credits section of the game (or download site, etc.):
Original (fill in the blank theme) assets: Brackeys @ devassets.com
The cool part of this is, if anyone does look into it, they’ll be able to see how your final version is different from the originals. 🙂