We can pretty much already do this by going to Admin CP > Forum Settings > Forum Title. You can use tags such as <b> and <i> in there too (http://theplayground.smfforfree2.com/index.php  my test site so you can see my Welcome title). 

My ? is....since all the initial welcome emails, emails people get when they have it set to notify them via email about PM's, etc, pull from this section and appear as the "From" heading in those emails, does your code affect that as well? 

I didnt think it would because it does not actually change the "forum title" field.   It only replaces the board name in that catbg area    You'll notice your forum name will still be the same just above the first board on your forum.

But.. I tested it at my mysmf.com test site.   Set it up.. sent myself some pms.   They come in fine, as they should 

Ok, the main reason why I made this is because if you do use HTML where you can change it without use my code, it shows it up at the top of your browser because it acts like it is part of the title.