One thing to keep in mind, a license is good to run an Eggplant instance, concurrently. So you can buy one GUI license and one CLI Only license, queue up sequential runs of scripts to run against a series of hosts, and continue to work on news tests while known working tests crunch and report away. This scenario would be what we call a Dual Stream.
If you get to the point where you are in need of more concurrent testing to occur, maybe running on 2+ Mac systems, testing against one current SUT each, more CLI licenses for those other hosts would be in order. In this case, with one developer, and possibly running on multiple concurrent hosts running tests, your needs would dictate the purchase of what are called 4 packs (1x GUI, 3x CLI Only).
And as you scale bigger, more rollout, more legacy regression testing, and possibly with more development test folks in your squad of developers, you may want to buy multiple GUI and dozens of CLI licenses. If you are going to develop a business model where you run tests and get paid for it, this is where business really gets started.
In the end each customer needs are unique, and different. That is why we don’t usually talk about this on the forums, but we highly recommend you talk to the Redstone Sales Group. They will be happy to sit and chat with you about what your very specific needs are, and how each licensing offering we have can be taken or combined to meet your business model.