The companies should be able to deduct it fully.

The museum aspect, non profit status etc doesn't matter. It's a legitimate marketing expense - they're paying the money to get on the front page of The Oatmeal, the same as if it went straight in The Oatmeal's pockets.

it depends and the amount can vary. I buy season tickets for my colleges football team and the seats I request have a minimum donation value required with them. all goes to a 501 3c, but if I recall its deductible at 70% of donation value.

Wouldn't it be like making a pledge to a local public broadcaster? You get gifts for those, but they are still tax deductible.

The last time I checked, if you receive something for your donation, you have to subtract the value of whatever you received from your total donation amount. You can then claim that difference as a deduction on your taxes.

Example: Donate $100 to PBS and receive a $10 CD. Subtract the value of the CD from the donation: $90. You can claim a deduction of $90 on your taxes.

But in the case of a corporation, treating the whole thing as a marketing expense is probably easier and would yield the same result.

[I'm not a lawyer or tax accountant or any other kind of authority on taxes. Check with the IRS or competent council before filing your taxes!]