The FCC has some very strict rules on unincorporated associations.
Applicants claiming to be unincorporated associations must include a letter signed by an attorney licensed to practice law in the state involved that demonstrates that unincorporated associations are recognized as non-profits in the state. In addition, there must be a statement showing how the organization's structure is consistent with the state law. Unincorporated associations must also include a description of any actual activity the unincorporated organization engaged in prior to the filing of the LPFM application.
References:eligibility, incorporated associations