They won't send a 1099-Misc for payments made by PrePaid Card systems. When they pay by other than cash or check, the payor doesn't need to report it. The Payment Processor would be reporting it via 1099-K, and the threshold is $20,000 and 200 transactions.

This is Other Income. it doesn't "go either way" because all income is reportable and taxable, even if from an illegal activity. Only explicitly exempt income is not taxable.

And this is not a Donation. The fluid you sold to BioLife is not you, donating. There are arguments made that you are being paid for your Time, but that would be taxable as well. And Pub 526 has this:

Not Deductible as Charitable Contribution:

Value of your time or services

Value of blood given to a blood bank