There is a page in Knowledge base entitled: "Project5- Free Stuff!" last updated 3/31/2016 (I tried attaching the url here, but it wouldn't stick for whatever reason, so if you just search KB for Project5, you will see it in related pages), and none of the download links are active anymore....?

I am not sure what is in that set of downloads, but there are also some P5 downloads at Patch Arena.

Here is the list of downloads.  The links seem to have expired, though.  It's been some years since the user group was active.  http://www.cakewalk.com/Support/Knowledge-Base/20090612/Project5-Free-Stuff
 
Here is the Project5 page downloads page at Patch Arena.
http://patcharena.com/downloads/index.php?subcat=108&ENGINEsessID=e326e0bf398d9da32c259faaa1c14722

It looks like most of that stuff is still available at Patch Arena, except for the SFZ player.  But that is still included with Sonar.