OpenStack is Apache-2 licensed. This license does not place restrictions on usage, so you don't need a special license to use it for commercial purposes. (IANAL, etc.)

The simple answer is that provided by @ttx: the software developed within the OpenStack project is licensed under the terms of the Apache Software License version 2 which is an approved open source license, meaning that the license complies with the Open Source Definition and with the Free Software Definition (free as in freedom). This means that you can use OpenStack (and any software that is licensed with licenses approved by OSI and FSF) for any purpose and without limitations.

If you get OpenStack from other distributors though you may want to make sure that the licenses of the extra pieces of software added on top of the software distributed by OpenStack Foundation don't add any restrictions. Maybe if you tell us exactly where you're getting OpenStack from we can give you a more precise answer.

I'm not lawyer, this is not a legal advice.