The download links can be found in our Knowledge Base:
http://portal.smartertools.com/kb/a2930/whmcs-provisioning-module-for-smartermail.aspx
http://portal.smartertools.com/kb/a2935/whmcs-add-on-module-for-smartermail.aspx
The titles of the articles don't exactly match, so I'll get that updated. You can see what each does from the bullet point list in the KBs though.