Wikipedia:GFDL

GFDL is the GNU Free Documentation License, the copyright under which Wikipedia formerly published.

Wikipedia articles:
 * Merge and delete – Why merging and the deleting the original page is normally not permitted under GFDL
 * Wikipedia copyrights
 * Copyright disclaimers on images
 * What the GFDL is not

Use of Wikipedia content in other works:
 * Reusing Wikipedia content
 * Verbatim copying under the GFDL

Full text:
 * Full text of the GNU Free Documentation License