Hello,
Sorry for the late reply, we were on holiday.

Greenstone 2.83 (gsdl 2.83) was not coded for 64 bit machines. However, there
is source code that's targeted at 64 bit machines which you can get from Greenstone's
SVN (SVN is a version control system).

The URL is:
http://svn.greenstone.org/main/branches/64_bit_Greenstone/greenstone2

And if you want GLI as well, then after checking out the above, you want to
go into the greenstone2 folder that you just checked out and checkout GLI here
from the URL:
http://svn.greenstone.org/main/branches/64_bit_Greenstone/gli

Finally, to compile, you would run the following 3 commands:
./configure --enable-apache-httpd
make
make install