Well i know you are going to ask why their is post for de-supported product. My answer will be who knows when you need the old version. and their is proverb Old is good. to download oracle forms 6i use the following link
From oracle website you won’t find the link. As of now only the latest version 11g and 10g is available for download.
Note :- Direct link won’t work out. It will throw some licence agreement error. To avoid error first login to to oracle website then click the link.