I've read this note about the short_open_tag option on http://www.php.net/manual/en/configuration.php :
"Tells whether the short form (<? ?> ) of PHP's open tag should be allowed. If you want to use PHP in combination with XML, you have to disable this option. If disabled, you must use the long form of the open tag (<?php ?> ).

Maybe you'll want to take account of it for the next UBBT releases.

Two and a half years later UBBT still uses short tags. It would be nice if they'd get updated to full tags.

The next-generation product uses the full open tag.