The Apple Developer Enterprise Program License
Agreement, linked from
https://developer.apple.com/terms/ (Apple ID login required), makes it VERY clear that the Enterprise Program is intended "for in-house, internal use applications". This point is reiterated multiple times throughout the introduction, and is later made more explicit:
> "Internal Use Application" means a software program (including extensions, media, and Libraries that are enclosed in a single software bundle) that is developed by You on a custom basis for Your own business purposes (e.g., an inventory app specific to Your business) for specific use with an Apple-branded product running iOS, watchOS, tvOS, and/or macOS, as applicable, and solely for internal use by Your Employees or Permitted Users, or as otherwise expressly permitted in Section 2.1(f). Except as otherwise expressly permitted herein, specifically excluded from Internal Use Applications are any programs or applications that may be used, distributed, or otherwise made available to other companies, contractors (except for contractors who are developing the Internal Use Application for You on a custom basis and therefore need to use or have access to such Application), distributors, vendors, resellers, endusers or members of the general public. For the sake of clarity, Internal Use Applications do not include third-party applications even if some customization has been done.
There's other damning bits later in the license agreement, including:
> You must provide clear and complete information to users regarding Your collection, use and disclosure of user or device data, e.g., a description of Your use of user and device data in the Your Internal Use Application.
and
> Notwithstanding anything to the contrary in Section 3.3.9, You and Your Internal Use Application may not use the Network Extension Framework, or any data or information obtained through the Network Extension Framework, for any purpose other than providing networking capabilities in connection with Your Internal Use Application (e.g., not for using an end-user's Internet traffic to serve advertising or to otherwise build user profiles for advertising).