The Sage development team still intends to support Solaris on x86 and SPARC 
(and regularly test on these platforms), but simply do no longer offer 
binary distributions of Sage for these. 

read more here:
https://groups.google.com/forum/#!topic/sage-devel/nDmmUzxiS3E

=== snip ===

content of former notes.txt about the files:

<div style="margin: 15px 0 20px 0; padding:0; font-size:115%">
The Solaris binaries are compressed and are available in two forms. If your SPARC system has the 'p7zip' command, which is standard on recent Solaris 10 releases, then it is recommended you download sage-...tar.7z as it is considerably smaller than the gzip compressed file. Otherwise you can download the .gz file, build pk7zip yourself, or install Sun patch 137477.
 
<pre> 
$ p7zip -d sage-....tar.7z (if you used the recommended .7z file) 
$ gzip -d sage-....tar.gz (if you downloaded the larger .gz file)
</pre> 
 
Sun's version of tar will not extract the binaries, so use the GNU tar.
 
<pre> 
$ /usr/sfw/bin/gtar xf sage-..tar 
$ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/sfw/lib 
$ export LD_LIBRARY_PATH
 
Change to the directory where the files were extract, then run
 
$ ./sage 
</pre> 
 
More detailed instructions can be found on the Sage Wiki at 
<a href="http://wiki.sagemath.org/solaris-binaries">solaris-binaries</a>.
</div>