In private group, can a new user see some code without charging you a licence?

Hello. We have an enterprise group, with starter package.

We would like to add some more users on some specific subgroups or projects, like partners and suppliers. From what i’ve read, it seems that a new user that is guest only is free of charge, but if he is reporter or more, an extra licence fee is charged.

It is possible, on a private group/project, to add someone so that he can see the files & code, but without the extra annual licence? Since being guest in private repos seems to prevent you from seeing any files… Is the licence counted monthly or annually if we only add the person, like, for a short duration (2 weeks)?