The short answer is no, English is not a mandatory requirement for approval into the sovrn exchange. We work with thousands of sites from around the world in many different languages. We do have other requirements in place to ensure that our exchange remains one of the cleanest and most trusted worldwide, however.
I would love to help you submit your site to our Operations team for vetting! Simply visit meridian.sovrn.com, provide the requested account information, and read through our Publisher Agreement. From there, you will be able to submit your site and receive an automated response within 24-48 hours with an updated account status. If you have any individual questions please do not hesitate to reach out directly at firstname.lastname@example.org.