A reuse licence specifies which uses of the material are allowed by the copyright holder concerned (for example posting the material on other websites, provided that the source is acknowledged) and which uses require permission.
And if commercial use of the material is allowed by the copyright owner.
One of the most well known type of reuse licenses are Creative Commons (CC) licenses, these are free and internationally accepted.
Creative Commons allows creators to add a license to their work so they can protect their work from misuse.
And so they can share their work, without people having to ask for permission for the use of the work.
Creative Commons have created 6 licenses that can be added to a work.
Please view this webpage for more information on the different kind of CC licenses that are available.
The website of Creative Commons organization also offers you the chance to find the works that have a Creative Commons license.
Via this link, you can search for materials that have a creative commons reuse license.
By using a source with a reuse license you will reduce your chances of violating copyright because the copyright owner has already given permission for re-use.
Wanna Work Together? from Creative Commons on Vimeo.