The calender can be downloaded from
www.fmods.com. In terms of editing, however, you are limited. The link you posted is of a domain phpBB forum, not a Forumer one. Since Forumer does not give out FTP access, you can not link the calender like that person did. You can, however, put the HTML for the calender in the description of one of your forums. The calender, as I said before, can be found at the above link.