I found these lines in ETinyMCE.php file:
// avoid URL headaches $options['relative_urls'] = false;
The comment says, to avoid headaches, but honestly I think it is the contrary. With relative_urls = false, absolute URL's are used wherever a link appears, which is bad, specially if the content is uploaded using the development machine. When copying the database to the production server, all relative links will be pointing incorrectly to the development server (for example, images).
What headaches are the author of the extension talking about?