Can I call a cURL resource in Freemarker component?

Are you trying to reach an external API (not the community API)? If so, I think there is only one way to do that. You have to use http.client.request from a custom endpoint.

http.client.request (khoros.com)

Tutorial: Integrate with a third-party REST API (khoros.com)

If that's what you are trying to do, I can share some code.