If I recall correctly, a gzfile descriptor must refer to a file on your server.
It is not exactly like fopen(), in that fopen could handle the url that is passed.
I may be wrong, and have been before... but perhaps you should try this:
<?php
$filename = "http://server.path/to.file.gz";
$fd = fopen($filename, "r");
//name our path, open the file.
$fileinput = fread($fd, filesize($filename));
fclose($fd);
//get the data, hold it in a local variable
$ucfile = uncompress($fileinput);
unset $fileinput;
//decompress string holding compressed data,
//drop the temp file, so as to not use more
//memory than necessary
echo $ucfile;
//may be a lot of data, but hey, at this
//point you can buffer it however you like.
?>