Most open is Public Domain –Not under copyright protection
CCO is the nearest you can come while work is under copyright
Legally, you don’t need to give attribution to these…
but I suggest using attribution or citation whenever you use borrowed content, as a professional best practice.
CC4.0 –attribute/cite source – do what you want - can sell result.
SA Share Alike – attribute/cite source- do what you want
but keep same License – can sell result.
NC Non-Commercial - attribute/cite source – do what you want
– Must not Sell / NOT for commercial use
ND is NO Derivatives…so you can’t just do what every you want,
- attribute/cite source - can make copies and share as-is
– you can sell