Are shared logins supported/allowed or is an enterprise plan the only option for multi-user accounts?

Are the listed plan prices per-user or per account?

My department splits responsibilities across multiple users. I typically manage the creation of a form/survey, another person manages the responses and analysis. A 3rd handles occasional reporting and generation of charts. And so forth. 

The help article https://www.jotform.com/help/232-How-to-Share-Forms-with-a-Sub-Account-User would have been exactly what we were looking for, but alas it doesn't look to be an option. 

Without going to an Enterprise plan, would each user need to have a separate paid plan to comply with JotForm's ToS? Are we allowed to have a single plan and log in that is shared among all our department users (who typically would never be in there at the same time)?

If you want to keep only one account and have a paid plan to it or you want to share the credentials to different department then you can do it.

Unfortunately, it is not possible to add sub-users to your account, it is only possible in the Enterprise plan.

Let us know if you have further questions.

Thanks.