Are you a private pilot looking to use it for training? The $200 P3D licence is for you. Student or staff in K-12 or undergraduate education institution? Go for the academic licence. Finally, if you are developing add-ons to be used by one of these first two groups, the developer licence fits. Their EULA and licence breakdown on their site is quite clear. And if it isn't clear, talk to LM and/or a lawyer.And therin lies the confusion - if I am using it to learn to fly AND I enjoy learning - does that constitute entertainment?
Those that are just interested in learning about how aircraft and aviation work, taking screenshots etc. but will never actually use it in support of actually flying or one of the categories LM specifically lists, do fall into the "entertainment" category and need to look elsewhere. Every academic licence I have seen has always involved being a student or staff attending or working in an education institution. Some are more thorough at verifying it, but the requirements have always been very similar. Just being interested in learning has never been enough to qualify.