CRM is licensed on a server and user licence model. You need one server licence for each server that CRM is installed on (you can install CRM on more than one server for resilience and performance reasons) and you need one licence for each named user.
You may have access to a development licence via MSDN (if you have a subscription or otherwise have access to MSDN). The other possibility is to use a trial licence (but they only last for 60 or 90 days).
Hope this helps.