Is PDO_OCI classed as ODBC?

I did post this question at Is PDO_OCI (PHP PDO using Oracle Instant Client) classed as ODBC? anonymously, but then it wouldn't allow me to comment on it so I registered and am posting it again here. I'm not sure what else to do.

I have a question that's been concerning me for some time.

We use Oracle at our company and we're about to upgrade to a newer release. I understand that Oracle have some additional licensing if you wish to connect to the database via ODBC.

My question is, we have a web application that connects to the Oracle database using PDO_OCI (PHP PDO using the Oracle Instant Client) - is this classed as accessing the Oracle database via ODBC?

In answer to this comment on the original question:

"I understand that Oracle have some additional licensing if you wish to connect to the database via ODBC" - where did you read that? The connection method is mostly irrelevant for licensing AFAIK

I'm not sure. I asked our software vendor to upgrade our Oracle database version and they are doing this but have raised a question "Do you access our database directly via ODBC? As this affects our licensing costs.".