[kh99]

I don't know exactly hwat change you want to make, but the part of postbit_legacy you want starts like this:

	<div class="postdetails">
		<div class="userinfo">
			<div class="username_container">
			<vb:if condition="$post['userid']">
				{vb:raw memberaction_dropdown}
				{vb:raw post.onlinestatus}
			<vb:else />
				<span class="username guest">{vb:raw post.musername}</span>
			</vb:if>
			</div>

That's the part that shows either the username with a dropdown menu, or Guest. If you haven't looked at templates before, it's really just html, but with some special tags for "if" statements and variable replacement.