StartSSL certs are not free to commercial entities.
Unfortunately, you are factually wrong. Their Class 1 certs used to be free for commercial purposes up until 2012, but that policy changed back then. See StartCom Certificate Policy & Practice Statements (warning: PDF) section 3.1.2 "Classes of digital X.509 Certificates" paragraph 1. Quoting from there (emphasis mine):
Class 1 Certificates provide modest assurances that the email originated from a sender with the specified email address or that the domain address belongs to the respective server address. These certificates provide no proof of the identity of the subscriber or of the organization.
Class 1 certificates are limited to client and server certificates, whereas the later is restricted in its usage for non-commercial purpose only. Subscribers MUST upgrade to Class 2 or higher level for any domain and site of commercial nature, when using high-profile brands and names or if involved in obtaining or relaying sensitive information such as health records, financial details, personal information etc.