Updating ClamAV on OS X Server >= 10.5.6
A tutorial on how to properly update ClamAV on Mac OS X 10.5.5 Server or greater. By Athanasios Alexandrides
Download “Updating ClamAV on OS X Server 10.5.5 or greater” (PDF File)
The purpose of this document is to provide instructions on how to update the version of ClamAV included with OS X 10.5.5 Server or greater. DO NOT use these instructions for 10.4.x Server. A separate tutorial is available for 10.4.x.
It will guide you through updating to the latest stable version of ClamAV without breaking Server Admin functionality. The new version will be installed alongside Apple’s. Thus, it will not be overwritten by Apple SW updates.
Although the Apple included version of ClamAV is suitable for most users, there are situations where one might need to update. A common reason is to take advantage of the latest security fixes.
This document is written for Mac OS X 10.5.5 or greater.

Are these instructions likely to be updated since SourceForge is now persona non grata and the download directory address has changed?
No, they will not be updated since Mac OS X 10.5 is not supported anymore. You should be able to simply substitute the download links.