I am trying to transform Web addresses with GET variables from something similar to

http://domain.com/?username=john

to

http://domain.com/john

using following a articles here and here.

While using example within the first article (having a slight modification) - RewriteRule .* index.php - I've become that to operate. The very first issue is, I still wish to have the ability to access another files within the same directory. Therefore the nearest I have become to date is RewriteRule index\.php/(.+) index.php?username=$1, that is still not ideal because I'm not going the filename within the URL, there is however one other issue. index.php is placed because the DirectoryIndex, and that i have no clue how you can match that.

I am still greatly a novice at setting up Apache, so any assistance is greatly appreciated.

Try something of that nature

RewriteEngine on

RewriteCond %{REQUEST_FILENAME} !\.php$
RewriteCond %{QUERY_STRING} \buser=\w+
RewriteRule .* user.php [L]

put rather than user.php the title of the script.