You haven't mentioned which ASE version you're looking for so I'm going to assume a newer/recent version of ASE 15.7 is sufficient ...
For quite awhile now all ASE downloads (IR, GA, EBF, SPxxx) have contained the entire code line (ie, you don't have to find a GA release and then apply a smaller/delta ebf patch file to get the latest version).
If you've got access to the EBF downloads @ sybase.com you should be able to download a recent copy of ASE 15.7 for Solaris/x86. During installation just pick the developer license version (the install will generate a generic *lic file for the developers version).
--------------
While there may be a way to download the file from the SAP website(s), I wouldn't have a clue since a) the SAP websites are poorly-designed/confuising and b) SAP is clamping down pretty hard on what Sybase related downloads are available and to whom.