I am developing an online store for my client. The application uses OpenCart as the back-end CMS and a theme (under GPL as well) at the store front. Is it legal to change the copyright notice for both admin and store front sites as follow?
"Copyright 2018 <name of client company>"
I know that GPL is a license for free software that requires the GPL license to be preserved for distribution, however I do not fully understand all of its implications, especially the following text in the GNU GPLv3.
I am not sure if this only requires attribution in the source code or copyright notice on the display of the site as well.Requiring preservation of specified reasonable legal notices or author attributions in that material or in the Appropriate Legal Notices displayed by works containing it
Notwithstanding any other provision of this License, for material you add to a covered work, you may (if authorized by the copyright holders of that material) supplement the terms of this License with terms:
a) Disclaiming warranty or limiting liability differently from the terms of sections 15 and 16 of this License; or
b) Requiring preservation of specified reasonable legal notices or author attributions in that material or in the Appropriate Legal Notices displayed by works containing it; or
c) Prohibiting misrepresentation of the origin of that material, or requiring that modified versions of such material be marked in reasonable ways as different from the original version; or
d) Limiting the use for publicity purposes of names of licensors or authors of the material; or
e) Declining to grant rights under trademark law for use of some trade names, trademarks, or service marks; or
f) Requiring indemnification of licensors and authors of that material by anyone who conveys the material (or modified versions of it) with contractual assumptions of liability to the recipient, for any liability that these contractual assumptions directly impose on those licensors and authors.