Someone with more knowledge of SQL Server Anywhere may want to correct me, but I don't think it's permitted to store passwords in a DSN. File DSN's are stored in a simple text file, and User/System DSN's are stored in the registry. This would allow for a tremendous security hole whereby anyone with access to your files could gain access to your secure database by reading your password from these files.
I've tried storing passwords in DSN files by manually adding them just to see what would happen, and they seem to be ignored at connection time.
Hope this helps!
~Warren