Do I need to have the same number of JIRA Software and JIRA Service Desk licenses?

Under the new model released last year, you only need to purchase Agent licences. Agents are people that typically man the service desk and own the Service Request, the work to fix the request can be managed within JIRA as tasks linked to the SR. eg you might have a 500 level JIRA licence but may only need 10 agent licences for y our IT Service Desk people.