Licence types

Hi All,

Quick question as I couldn’t seem to find a definitive response.

I’ve created a theme I’d like to release (for free) but would like to keep a single link back to my site in the footer of the theme.

As long as it’s permitted, I’d also like to allow people to edit/improve on the theme but not redistribute it.

Do you know what sort of release licence would be approprite for this?

Many thanks