You can specify title for home page using $this->template == 'qa'
There are two ways to do. Firstly:
In qa-include/qa-theme-base.php
search this code and change
function head_title()
{
$pagetitle=strlen($this->request) ? strip_tags(@$this->content['title']) : '';
$headtitle=(($this->template == 'qa') ? 'YOUR CUSTOM TITLE HERE' : (strlen($pagetitle) ? ($pagetitle.' - ') : '').$this->content['site_title']);
$this->output('<TITLE>'.$headtitle.'</TITLE>');
}
Change YOUR CUSTOM TITLE HERE with whatever you want. This will display your custom title on Home page only