Green flags:

• copyleft license (GPL or better AGPL) + they accept contributions without contributor license agreement
• code written by many people who personally own the copyright
• active community

Yellow flags:

• permissive license
• business model which can’t be really be sustainable with a shit-free product

Red flags:

• VC funding (implies enshittification in future because of profit maximization)
• proprietary license
• project does not take contribution from the outside or asks to transfer copyright or sign some document (CLA)