To avoid the version check you can edit the wpmovielibrary.php file at the root of the plugin's folder, and change line 41 from define( 'WPMOLY_REQUIRED_PHP_VERSION', '5.3' ); to define( 'WPMOLY_REQUIRED_PHP_VERSION', '5.2' );, but be careful: the reason PHP 5.2 is excluded is that the plugin uses some PHP > 5.2 features; running it with 5.2 has a good chance to end up with errors.
Anyways, I hope you get that PHP issue solved: PHP 5.2 is completely obsolete (5.3 too, for that matter) and softwares will progressively drop it… WPMovieLibrary doesn't use extensively recent PHP versions, but it may in the future, so support outdated version of PHP will become a real problem.