I have a squidguard rpm originally from the "green computer" site.  I believe this RPM is built from Darrell May's.  It works for 4.1.2.  I use it on 5.0.  I have not been able to get it to work on 5.1.2.  I can email it to you if you want this version of squidguard.
Note:  In 5.0, the web based tool for squidguard does not work from the server-manager link that gets installed.  Instead, I use a browser and point it to the squidguard ibay.  I also put a password on this ibay from server manager so it can be available from anywhere with password protection.  
For my system, I use this address from my lan:  
http://smename/squidguard/  or from the internet:  
http://xxx.domain.com/squidguard/  I then use squidguard as the username and enter my password to access the ibay.  Note that Ibay usernames are the same as the ibay name.
RS