In order to see the free/busy time for these users you will need to add a default free/busy server to the Search Location field of the Free/Busy Options property sheet. This must be done in Outlook for each client wishing to use the Free/Busy function.
The Free/Busy Options property sheet is accessible by selecting Tools | Options and pressing the Calendar Options button and then pressing the Free/Busy Options button. Note, you must replace WorkGroupShareServer with the IP address or hostname of the computer which runs WorkgroupShare.
The Outlook Calendar for each user who wishes to publish free/busy information must have been shared in the Outlook client and synchronized to the WorkgroupShare server.