I have modified some files of an open source project under GNU GENERAL PUBLIC LICENSE to add some specific features. I would add the same license for the part of the code written by me. How i should do this? What is the preamble that have to be added to files modified? Thanks
Usually because of the Gnu GPL definition, if the code is under GPL license and if any changes made to the code then the total code should be licensed under the GPL compatible license. But usually everyone license the code under the same GPL license.