Oracle DB license for only non-production environments
Yes you do.  If you install the Oracle software you need to pay for it.  However numerous exceptions exist including


you can use Oracle Express 11g for free
your customer may have licencing provisions that apply to you


Either way, do not take anything from my answer or anyone else's answer as valid.  Oracle licencing  is complex and a final word can only come from them.  Contact  your representative and ask for clarification.