What is the correct way to get a Sitefinity.lic for developm

As a contractor, I do not have a lic. file for every version of sitefinity and any add-ons.
What is the correct way to develop/test  locally and then deploy to a customer site (which has the proper Lic. ) ?

Hello Tim ,

Thank you for using our services.

You can either work on the project locally (and you will not get a license error), or you can host the website on a development server, using a subdomain. Keep in mind that from 6.0 all subdomains need to be explicitly added to the license file. If you'd like to take advantage of this approach, you can drop us a line and let us know which subdomain you'd like to have added to the license file. If you still don't have license you can host the website on a server and run it on its IP. You will get Trial messages on each 20th request of a page, but since the purpose of the website is development, and the customers will not have access to this website, you shouldn't experience any problems. Keep in mind that if you host the project somewhere you need to be sure that your environment is configured properly, so that you will not get any server errors (because the project can't find its service files). You also need to set WorkflowBaseUrl, according to this this KB and configure your HOSTS file properly:
In the server node where the site is running configure in windows hosts file that the IP of the server is mapped to the domain, then for WorkflowBaseUrl enter http://domain.com