Sun Microsystems offered Solaris 8 in the free binary license program. You could download Solaris 10 for free after registering. Solaris 8 is no longer available on the Sun site. If you have an 18 Gig drive on your machine, you can get Solaris 9 to run on a Sparc 20, although it is not supported. Solaris 10 will not run on Sparc 20's (or even Ultra 1's). Ultra 2's and beyond will run Solaris 10. I have no knowledge of Solaris 11. You may be able to find a copy of Solaris 8 somewhere. In March 2014, a google search of sol-8-hw4-sparc-v1.iso showed up a couple of places you could download the iso files.
As an alternative, the freeBSD has a Sparc port which I have loaded on an Ultra 1. I am not sure how stable it is.
All of the information on this page can be found on the Sun web site with a little digging.
If you want to download the disks, you can download the disk images to your PC and convert the images to a CD there. You should have a DSL or Cable modem as the images total about 800 Megabytes. There are three disk images that you download one at a time. The first creates a CD which is bootable from a Sparc and installs the Solaris 8 operating system. It is called the install CD. The second is all the packages found on the install as individual packages. Maybe? This CD is not used during the initial installaiton. It is calls Solaris Software Volumme 1. The third CD is called Solaris Software Volume 2 and contains assorted supplimentary software like zip, bzip, and other utilities. This CD gets called for during the install.
Once you've downloaded the images onto your PC you will need to create the CD's with a CD Writer. First you will unzip the compressed images on your hard drive and then rename each of the images to have the extension .iso so the CD burner program will properly recognise it. If you are using Adaptec EZ CD Creator or Nero Burning ROM, from the file menu select "Create CD from Image" and point the open dialog with pops up at the .iso file. In the Adaptec program you have to change the filter in the open dialog from .CLI to .ISO. Then you create the CD's
To boot the Sun from CD, the first thing you will need is a CD on the machine. The machines we have did not come with one. The page on adding hardware to your Sun discusses your options with respect to adding a CD.
You can do the install serveral ways. The one I have tried and used successfully is to do a full install to an empty disk (the install makes it be empty to start).
Note:The install comes with 3 CD's. An install CD, a Software CD 1 and a Software CD 2. There are also some documentation CD's. The obvious thing to do is boot from the Solaris install CD. This puts you into some sort of web install which I have never gotten to work correctly. Boot from the Software CD 1 If you wonder why I coded highlighted this in red is that after a disk failure, I spent three days trying to install starting with the install disk before I mistakenly booted from the software disk 1 and got things to work.
While I prefer pkg-get to add software to the Sun, There are other ways to get free software for the Sun. Most of the GNU programs have been ported to the Sun Solaris environment. There is a Download freeware for Sun (gcc, gdb, ddd, etc.) site with several mirror sites you can use to download software. Most of these packages for Solaris 8 are set up as Sun Packages. To install one of these packages perform the followint steps:
The Ce editor and terminal emulator is also available for the home network