Comment: The last commit to the CVS for this package is 4 years old, and I find it reliably crashes Allegro Common Lisp (ACL 8.2, 64-bit, on both Linux and Mac OS X). Claims to use CFFI, but references the UFFI package, and it's the :uffi library that's loaded by cl-syslog.asd. Update: Looks like it's only the version in CVS that has been updated to use CFFI; the tarball on the common-lisp.net project page is still UFFI.
Comment 2: lhope cloned the 2006 CFFI version at https://github.com/lhope/cl-syslog.
Comment 3:UDP syslog support has been added to cl-syslog at https://github.com/mmaul/cl-syslog. Updated package is in the process of being submitted to quicklisp.
Quickdocs project page here