I've installed modern, then removed database, make new db, import schema.mysql and then tried to execute in phpmyadmin your install file with mysql queries.
It show error because of:
There is no table 'forum' (modern use 'forums') and you try to add column in not existing table (or .php script execute queries from last to first).
It show error because of:
PHP:
ALTER TABLE `forum` ADD `guild` int(11) unsigned DEFAULT NULL;