First to clear a few things up.

It is definitely not a gift. The people are sending you money only because you are providing them with a service.

And for tax purposes, it is not a "Donation". It has nothing to do with the fact that you are soliciting the donation, as charitable organizations solicit donations all the time. For tax purposes, it is not a "Donation" because you do not have 501(c)(3) non profit status.

It is income. The question is then, is it "Business" income, or "Hobby" related income?

Firstly, you haven't mentioned, but it's important to consider, how much money are you receiving from this monthly, or how much money do you expect to receive from this annually?

If it's a minimal amount, say $50 a month or less, then you probably just want to treat it as a hobby. Mostly because with this level of income, it's not likely to be profitable. In that case, report the income and pay the tax. The tax you will owe will be minimal and will probably be less than the costs involved with setting up and running it as a business anyway. As a Hobby, you won't be able to deduct your expenses (server costs, etc...) unless you itemize your taxes on Schedule A.

On the other hand if your income from this will be significantly more than $600/yr, now or in the near future, then you should consider running it as a business.

Get it clear in your mind that it's a business, and that you intend it to be profitable. Perhaps it won't be profitable now, or even for a while. What's important at this point is that you intend it to be profitable.

The IRS will consider, if it looks like a business, and it acts like a business, then it's probably a business... so make it so.

Come up with a name for your business. Register the business with your state and/or county as necessary in your location. Get a bank account for your business. Get a separate Business PayPal account. Keep personal and business expenses (and income) separate.

As a business, when you file your taxes, you will be able to file a Schedule C form even if you do not itemize your taxes on Schedule A. On Schedule C, you list and total your (business) income, and your (business) expenses, then you subtract the expenses from the income to calculate your profit (or loss).

If your business income is more than your business expenses, you pay tax on the difference (the profit).

If your business expenses are more than your business income, then you have a business loss. You would not have to pay any income tax on the business income, and you may be able to be carry the loss over to the next and following years.

You may want to have a service do your taxes for you, but at this level, it is certainly something you could do yourself with some minimal consultations with an accountant.