Simplify the following text for a Grade 13 native English-speaking person.
Original: This is a guide for using multiple licensing of one 's contributions made to Wikipedia so that they are in the public domain or licensed under alternative licenses in addition to the CC-BY-SA license ( and GFDL , often ) .
Simplified: This is a guide for using multiple licensing of one 's contributions made to Wikipedia so that they are in the public domain or licensed under alternative licenses in addition to the GFDL .