Sorry @Juerg - I'm a bit confused as to what you are asking...
As per our private message with by DM with @instacks on the RapidWeaver forum:
Pulse4 standalone has complete standalone relative paths with no problems. You can install in a sub directory or root.
Make sure to use <?php echo $path; ?> so something like:
<?php echo $path; ?>/asset/.jpg
You may also need to change the htaccess file to /subdomain/ in some cases / hosts for RewriteBase /
But linking from the Media folder considers the location and will adapt (relative) accordingly
So if you add photos in Blogs from the Media it will take care of these. Or use the relative link if hand coding.