I don't think Oracle has created one yet. Here is the full list: https://forums.oracle.com/forums/main.jspa?categoryID=84
I would check the above link regularly, as I would imagine, they will add Endeca there soon. For now, you may find this useful: http://www.oracle.com/us/corporate/acquisitions/endeca/support-1418464.html
Mehmet is correct, they have not yet been created, however they will be created as mos community forums, instead of on OTN, similar to the endeca eden forums.
If you have a technical question, and you are a customer feel free to log an SR and one of the Support team will be glad to help you.
Oracle Endeca Commerce Product Family: http://www.oracle.com/technetwork/apps-tech/commerce/endeca-commerce/overview/index.htm then click on the Community tab or: http://www.oracle.com/technetwork/apps-tech/commerce/endeca-commerce/community/index.html