Hello! Thank you for trying the game out. The art pack comes from humble bundle and has no restrictions on it, nor does it have an author specified. We did not mean to break the rules and if we did, please let us know how to fix this issue for possible future misunderstandings. Thank you again.
Viewing post in Raid Boss jam comments
The jam’s rules on credit are as follows: A. You have to credit all work (including CC0 assets, and even your own assets), and B. It must be accessible at the start of the game. I’m not a jam official, but you could try putting credits on the game page, maybe that counts? Regardless, my advice for the future would be to take a careful look at the rules before starting the jam (or really anything) since each jam is likely to have somewhat different rules from the last.
Also if you want to look for yourself I’ll provide a handy link to the rules: https://itch.io/jam/vimjam2/topic/1570354/official-jam-rules