Untested but like this, though you may need to tweak as desired:
Code:
<tr>
<td width="100%" class="smallfont">$value[title]</td>
<td style="white-space:nowrap;">
<if condition="THIS_SCRIPT == 'register'">
<label for="rb_1_$key"><input type="radio" name="gaz_sub[$key]" id="rb_1_$key" value="1" tabindex="1" title="$vbphrase[yes]" checked="checked" />$vbphrase[yes]</label>
<label for=\"rb_0_$key\"><input type="radio" name="gaz_sub[$key]" id="rb_0_$key" value="0" tabindex="1" title="$vbphrase[no]" />$vbphrase[no]</label>
<else />
<label for="rb_1_$key"><input type="radio" name="gaz_sub[$key]" id="rb_1_$key" value="1" tabindex="1" title="$vbphrase[yes]" <if condition="$newsletteron == true">checked="checked"</if>/>$vbphrase[yes]</label>
<label for=\"rb_0_$key\"><input type="radio" name="gaz_sub[$key]" id="rb_0_$key" value="0" tabindex="1" title="$vbphrase[no]" <if condition="$newsletteron == false">checked="checked"</if> />$vbphrase[no]</label>
</if>
</td>
</tr>