Whereas my team may have a number of members, there's usually an on-duty rotation where if the team is roped in to answer a question, it may be nice for other teammates to have a archive of said questions, but the on-duty should receive it in their work queue. In our organization, we have a mechanism to take email to a specific non-user email address and turn that into an internal ticket. Is there a way to add non-user subscriptions, or are non-users allowed to have GitHub accounts? Is there a different model that I should be considering instead?
The GitHub Terms of Service state:
A2: You must be a human. Accounts registered by "bots" or other automated methods are not permitted.
A4: Your login may only be used by one person - i.e., a single login may not be shared by multiple people - except that a machine user's actions may be directed by multiple people. You may create separate logins for as many people as your plan allows.
Further, the page on Machine Users clarifies A2:
This means that you cannot automate the creation of accounts. But if you want to create a single machine user for automating tasks such as deploy scripts in your project or organization, that is totally cool.
So if you are a human who is creating the registration, and the registration for what turns out to be a machine user that is only listening (that is, receiving e-mails) [and may have subscription etc. actions directed by multiple people], for the purposes described in the post, that seems fine. Further, from GitHub's perspective, this user account is not different from a person who's relatively inactive (passively receiving e-mail) and doesn't say much.
Alternatively, you could consider using the API.