Why do I get Call to undefined function updatedb()
drush updatedb is a valid command.

updatedb (updb)       Apply any database updates required (as with running update.php).


However, I'm not sure about using it in place of db_query.

In D7 you would use db_update there.

In D6, you're stuck with db_query

It looks like a syntax error in the module code, it probably needs to use D6 style db_query