Anyone (brand, retailer, manufacturer, service provider, individual) can apply to become a trainer or verifier as long as required criteria are met.  There is technically no limitation on who can fill out an application, however, the application is for those who wish to be approved to provide SAC approved services (verification, facility training). For those who are interested in completing training but not seeking to be an approved service provider (e.g. interested to learn new skills or for own personal knowledge), training modules will are available (link) and do not require an application form.