Primary keys are created as unsigned integers so there should be a way of creating unsigned integer fields (for foreign keys etc.):

Line 583, class.MySQLAdapter.php:

if(is_array($options) && array_key_exists('null', $options) && $options['null'] === false) { $sql .= ' NOT NULL'; }

becomes

if(is_array($options) && array_key_exists('unsigned', $options) && $options['unsigned'] === true) { $sql .= ' UNSIGNED'; }

if(is_array($options) && array_key_exists('null', $options) && $options['null'] === false) { $sql .= ' NOT NULL'; }

Line 231, class.MySQLTableDefinition.php:

$opts = array( 'null' => $this->null, 'default' => $this->default );

becomes

$opts = array( 'null' => $this->null, 'default' => $this->default, 'unsigned' => $this->unsigned );

This has been fixed and committed.

Thanks for the feedback.