I have to say that something happened to the file either when you downloaded it from my web site or when you transferred it to your Zaurus. The file is fine, as far as I can tell. From my Internet server command line:
bash$ file libdb2_2.7.7_arm.ipk
libdb2_2.7.7_arm.ipk: gzip compressed data, deflated, last modified: Tue Apr 6 01:56:41 2004, max compression, os: Unix
bash$ zcat libdb2_2.7.7_arm.ipk | tar tvf -
-rw-r--r-- root/root 4 2004-04-06 01:43:43 ./debian-binary
-rw-r--r-- root/root 134707 2004-04-06 01:56:32 ./data.tar.gz
-rw-r--r-- root/root 388 2004-04-06 01:47:37 ./control.tar.gz
It seems fine on the server and the same file installs on my SL-5600...