[dartho]

maybe - you basically have to add the following code into the footer template

<script type="text/javascript" src="{vb:raw vboptions.bburl}/clientscript/vbulletin-core.js?v={vb:raw vboptions.simpleversion}"></script>
<div>
	<form action="{vb:raw vboptions.forumhome}.php" method="get" id="footer_select">
		<vb:if condition="$show['languagechooser']">
			<select name="langid" onchange="switch_id(this, 'lang')">
				<optgroup label="{vb:rawphrase quick_language_chooser}">
					{vb:raw languagechooserbits}
				</optgroup>
			</select>
		</vb:if>
	</form>
</div>
</vb:if>

but some of that code would usually be shared with the quick style chooser.

If you do not use the style chooser, search for the following and replace it with the above code

<vb:if condition="$vbulletin->options['ls_default_style_link']==3">
<script type="text/javascript" src="{vb:raw vboptions.bburl}/clientscript/vbulletin-core.js?v={vb:raw vboptions.simpleversion}"></script>
<div>
	<form action="{vb:raw vboptions.forumhome}.php" method="get" id="footer_select">
		<vb:if condition="$show['quickchooser']">
			<select name="styleid" onchange="switch_id(this, 'style')">
				<optgroup label="{vb:rawphrase quick_style_chooser}">
					{vb:raw quickchooserbits}
				</optgroup>
			</select>	
		</vb:if>
	</form>
</div>
</vb:if>

If you want both choosers, replace with this

<script type="text/javascript" src="{vb:raw vboptions.bburl}/clientscript/vbulletin-core.js?v={vb:raw vboptions.simpleversion}"></script>
<div>
	<form action="{vb:raw vboptions.forumhome}.php" method="get" id="footer_select">
		<vb:if condition="$show['languagechooser']">
			<select name="langid" onchange="switch_id(this, 'lang')">
				<optgroup label="{vb:rawphrase quick_language_chooser}">
					{vb:raw languagechooserbits}
				</optgroup>
			</select>
		</vb:if>
		<vb:if condition="$show['quickchooser']">
			<select name="styleid" onchange="switch_id(this, 'style')">
				<optgroup label="{vb:rawphrase quick_style_chooser}">
					{vb:raw quickchooserbits}
				</optgroup>
			</select>	
		</vb:if>
	</form>
</div>