Squad servers are operated by the community, mostly by gaming clans and similar organizations. But Squad uses a "server license" system where server owners must meet certain criteria (for example a minimum level of moderation) in order to be allowed to operate a server. Supporting the DLC is sure to be a requirement.
This system existed in Project Reality too, I believe in that game it outright prohibited you from even having access to the server executable without a license while in Squad it only applies to being listed in the client's server browser.