GNO is a large and complex system. There are many pieces to it; too many to list in detail here. There are, however, two major catogories of pieces. The first is the base distribution, the second are all the third-party ``add-ons''. (Some of the second category sometimes get moved into the base distribution). Normally, one would install the base distribution, then install whichever third-party applications are desired.
Currently, there are available two versions of the base GNO distribution. The first is version 2.0.4, which is the one last version released by Jawaid. It is relatively stable and easy to install, but has no TCP/IP support, a few known bugs, and is not getting any kernel updates. (Recent library updates can, to some extent, be used with this version.)
The second available version is 2.0.6. It is undergoing active development and therefore includes bug fixes to v2.0.4, as well as TCP/IP support in the kernel (it does not currently take advantage of Marinetti). On the other hand, it is still of alpha quality; it is difficult to install, has some incompatibilities with 2.0.4, and new bugs have been introduced. Once it has stabalized more, it will completely supercede version 2.0.4.
Both base distributions are available via anonymous ftp. Version 2.0.6 is also available in source form, including via anonymous cvs. See the respective Installation chapters on downloading these files.
Third party applications are available (among other places) from ftp://ftp.gno.org/pub/apple2/gs.specific/gno. Because this collection has grown so large, James Brookes developed the describedatabase (later maintained by Soenke Behrens and Devin Reade), which provides a description and other information on the various GNO utilities. Online interfaces to the database may be found at http://www.gno.org/~gno/describe/ or http://www.servtech.com/public/phoenix/computers/gno/index.html.