Key used to sign bison-2.4.3.tar.bz2 has expired

[Michael Harrison]

Hi, I downloaded and imported the keys from:
http://savannah.gnu.org/project/memberlist-gpgkeys.php?group=bison

but it seems that the key used to sign bison-2.4.3.tar.bz2 expired on 19 
January 2011:

$ gpg --verify bison-2.4.3.tar.bz2.sig bison-2.4.3.tar.bz2
gpg: Signature made Fri 06 Aug 2010 02:49:29 BST using DSA key ID 263DF280
gpg: Good signature from "Joel E. Denny <address@hidden>"
gpg: Note: This key has expired!
Primary key fingerprint: 6F2C 36CB 314C A6A5 0A44  391B C2DC 77AD 263D F280

$ gpg --list-keys 263DF280
pub   1024D/263DF280 2010-01-19 [expired: 2011-01-19]
uid                  Joel E. Denny <address@hidden>

The signature appears to have been verified successfully, so I'm not sure if 
this is a problem or not?