I’d venture it is because Firefox is developed by a for-profit corporation with hundreds of millions in revenue. So the split is: you can donate to the non-pro

I’d venture it is because Firefox is developed by a for-profit corporation with hundreds of millions in revenue. So the split is: you can donate to the non-profit organization, while the for-profit corporation only handles taxable income. The reason why it is split is due to taxes. Mozilla created the corporation after getting in trouble with the IRS. Edit: I haven’t kept up with Thunderbird for a very long time, but it looks like they’ve also moved to be developed by a for profit corporation, but a different one then the one that develops Firefox, so different people making different decisions. Also, donations to thunderbird are no longer tax deductible.