Open file templates/ja_template/templateDetails.xml, search and edit/remove the text:

<name>ja_university_t3</name>
 
	<version>1.0.0</version>
 
	<creationDate>17 Feb 2014</creationDate>
 
	<author>JoomlArt.com</author>
 
	<authorEmail>webmaster@joomlart.com</authorEmail>
 
	<authorUrl>http://www.t3-framework.org</authorUrl>
 
	<copyright>Copyright (C), J.O.O.M Solutions Co., Ltd. All Rights Reserved.</copyright>
 
	<license>license GNU/GPLv3 http://www.gnu.org/licenses/gpl-3.0.html</license>
 
	<t3>
 
		<base>base-bs3</base>
 
	</t3>
 
	<description>
 
		<![CDATA[
 
		<div align="center">
 
			<div class="alert alert-success" style="background-color:#DFF0D8;border-color:#D6E9C6;color: #468847;padding: 1px 0;">
 
				<a href="http://t3-framework.org/"><img src="//static.joomlart.com/images/jat3v3-documents/message-installation/logo.png" alt="some_text" width="300" height="99"></a>
 
				<h4><a href="http://t3-framework.org/" title="">Home</a> | <a href="http://demo.t3-framework.org/" title="">Demo</a> | <a href="http://t3-framework.org/documentation" title="">Document</a> | <a href="https://github.com/t3framework/t3/blob/master/CHANGELOG.md" title="">Changelog</a></h4>
 
				<p> </p>
 
				<span style="color:#FF0000">Note: T3 blank requires T3 plugin to be installed and enabled.</span><p></p>
 
				<p>Copyright 2004 - 2013 <a href='http://www.joomlart.com/' title='Visit Joomlart.com!'>JoomlArt.com</a>.</p>
 
			</div>
 
			<style>table.adminform{width: 100%;}</style>
 
		</div>
 
		]]>
 
	</description>

Please keep the mark-up because it may corrupt the installation package.

#1: JA T3v1 or non-JAT3 Templates:

Open file: templates/ja_template/html/mod_footer/default.php, remove/change the text. Kindly keep the HTML mark-up.

<?php
 
 
 
// no direct access
 
defined('_JEXEC') or die;
 
?>
 
<small><?php echo $lineone; ?> Powered by <a href="http://www.joomlart.com/joomla/templates/ja-lens" title="JA Lens"  rel="nofollow" >JA Lens</a> - Designed by JoomlArt.com.</small>
 
<small><?php echo JText::_( 'MOD_FOOTER_LINE2' ); ?></small>

#2: JA T3v2 Templates:

Open file: templates/ja_template/html/mod_footer/default.php, remove/change the text. Kindly keep the HTML mark-up.

		
<?php
 
 
 
// no direct access
 
defined('_JEXEC') or die;
 
?>
 
<div class="module">
 
	<small><?php echo $lineone; ?> Designed by <a href="http://www.joomlart.com/" title="Visit Joomlart.com!" <?php echo method_exists('T3', 'isHome') && T3::isHome() ? '' : 'rel="nofollow"' ?>>JoomlArt.com</a>.</small>
 
	<small><?php echo JText::_( 'MOD_FOOTER_LINE2' ); ?></small>
 
</div>

#3: T3 Templates:

Open file: templates/ja_template/html/mod_footer/default.php, remove/change the text. Kindly keep the HTML mark-up.

		
<?php
 
 
 
// no direct access
 
defined('_JEXEC') or die;
 
?>
 
<div class="module">
 
	<small><?php echo $lineone; ?> Designed by <a href="http://www.joomlart.com/" title="Visit Joomlart.com!" <?php echo method_exists('T3', 'isHome') && T3::isHome() ? '' : 'rel="nofollow"' ?>>JoomlArt.com</a>.</small>
 
	<small><?php echo JText::_( 'MOD_FOOTER_LINE2' ); ?></small>
 
</div>

#1: JA T3v1 Templates:

Open file: /templates/ja_template/layouts/blocks/footer.php, find this code to remove:

 Powered By T3 Framework

#2: JA T3v2 Templates:

Login to Admin area, go to manage the template, select Profile tab, choose one profile to edit, at General Settings section set T3 Logo to "Not Show".

#3: T3 Templates

Login to Admin panel, go to: Extensions >> Template Manager, open JA template. In the admin area of JA Template, select tab: General, now disable option: Show T3 Logo.

An other way is using templates/ja_template/tpls/block/footer.php file. Open that file and you would see the code like this:

<?php if ($this->getParam('t3-rmvlogo', 1)): ?>
 
	<div class="col-md-4 col-xs-12 poweredby text-hide">
 
		<a class="t3-logo-small t3-logo-light" href="http://t3-framework.org" title="<?php echo JText::_('T3_POWER_BY_TEXT') ?>" target="_blank" <?php echo method_exists('T3', 'isHome') && T3::isHome() ? '' : 'rel="nofollow"' ?>>
 
			<?php echo JText::_('T3_POWER_BY_HTML') ?>
 
		</a>
 
	</div>
 
<?php endif; ?>

Remove it and T3 footer logo will be removed.

Normally, a template copyrights includes JoomlArt copyrights, T3 footer logo and Joomla copyrights. If you want to remove/change Joomla copyrights, please open the the language file of Footer Module. If you use English language, the file is: language\en-GB\en-GB.mod_footer.ini. Open that file then change language of "MOD_FOOTER_LINE2" as language of "MOD_FOOTER_LINE1" is overridden with template copyrights.

MOD_FOOTER="Footer"
MOD_FOOTER_LINE1="Copyright © %date% %sitename%. All Rights Reserved."
MOD_FOOTER_LINE2="<a href="/_QQ_"http://www.joomla.org"_QQ_">Joomla!</a> is Free Software released under the <a href="/_QQ_"http://www.gnu.org/licenses/gpl-2.0.html"_QQ_">GNU General Public License.</a>"
MOD_FOOTER_XML_DESCRIPTION="This module shows the Joomla! copyright information."

If you are using T3 BS3 Blank template, you will see the Bootstrap copyright in the footer. If you want to remove/change the info, follow the instruction.

The copyrights info is declared in the templates/t3_bs3_blank/tpls/block/footer.php file. Open that file and you would see the info:

<small>
 
  <a href="http://twitter.github.io/bootstrap/" target="_blank">Bootstrap</a> is a front-end framework of Twitter, Inc. Code licensed under <a href="http://www.apache.org/licenses/LICENSE-2.0" target="_blank">Apache License v2.0</a>.
 
</small>
 
<small>
 
  <a href="http://fortawesome.github.io/Font-Awesome/" target="_blank">Font Awesome</a> font licensed under <a href="http://scripts.sil.org/OFL">SIL OFL 1.1</a>.
 
</small>

You can change or remove, it's your call.