The least restrictive Creative Commons license among the ones you listed is CC BY (Attribution). This license allows others to distribute, remix, adapt, and build upon the work, even commercially, as long as they credit the creator.
In contrast, the other licenses impose more restrictions:
- CC BY-SA (Attribution-ShareAlike) requires that any derivative works be shared under the same license.
- CC BY-NC-ND (Attribution-NonCommercial-NoDerivs) allows others to download and share the work non-commercially but does not allow modifications or commercial use.
- CC BY-NC (Attribution-NonCommercial) allows for non-commercial use and modifications, but still restricts commercial applications.
Therefore, CC BY (Attribution) is the most permissive option.