Remove Joomla! is Free Software released under the GNU/GPL License.

To change or remove the "Joomla! is Free Software released under the GNU/GPL License." links from the joomla administration area we need to edit 3 files:
administrator/templates/khepri/cpanel.php
administrator/templates/khepri/index.php
administrator/templates/khepri/login.php

How To Change and Make Writing Copyright in Joomla

Copyright writing is usually located on the footer or the bottom of a site. If you are still using the default template provided by the joomla, then the default standard joomla copyright writing is usually like this.
Powered by Joomla!. valid XHTML and CSS.
To replace and modify to your liking, the steps are as follows:
Log into your Joomla Administrator page.
Select menu extensions >>> template manager .
Select and tick the check box template you use. Then click Edit .
Click edit HTML , then you will go to the Template page HTML Editor.
Then try to find the following code. (How to find a brief press shortcut: alt + f and enter text below)
id = "power_by"

Remove "Powered by Phoca Gallery" Text

Phoca Gallery is a fantastic open source extension for Joomla. It is a full featured photo gallery that is fairly easy to use. Phoca Gallery is open source GPL. By default Phoca Gallery puts a "Powered by Phoca Gallery" copyright line in the footer of every Phoca page. If it's your own website you might not mind giving credit to the developer as they deserve then it might be ok but when I've used it on a client website I have always been asked to remove it as it does look unprofessional. If you are going to remove it I would also suggest making a donation to Phoca Gallery as I have. This method shows how to remove the copyright from the 2.7.6 version of Phoca Gallery.
Youll need to install Phoca Gallery and navigate to your website folders via FTP...
1. Open the file administrator\components\com_phocagallery\front\views\category\view.html.php
Search for the long string around line 165 that begins with

Remove Powered by Phoca Guestbook

Best on My experience in developing websites with Joomla CMS some time ago that requires using the guestbook makes me have to find a suitable component guestbook. After a few components that I try so I made sure to use the Phoca Guestbook, but the results are less satisfactory because of the persistence of the words “Powered By Phoca Guestbook“, I do not miss going to Remove Powered By Phoca Guestbook for Phoca Guestbooks look more attractive.
Pocha Guestbook is the product of Pocha.cz, is one of the joomla component that serves to increase the Guestbook facility on the web that use Joomla CMS.

How To Remove Help Menu From Joomla Administrator's Menu

The First Thing to do this is:
Just go to the folder ...administrator >> modules >>mod_menu

Second thing :

Modify the file 'Helper.php'

For e.g. If you want to delete the 'Help Menu'
Go to /* Help SubMenu */ section of Helper.php file
Delete the text -->'Help'
$menu->addChild(new JMenuNode(JText::_('')), true);

This will hide Help Menu....

You can also change links, text...
For e.g.

$menu->addChild(new JMenuNode(JText::_('Your text'), 'http://www.anysite.com', 'class:help'));


I hope that these "tricks" help you along the way.....