Reading the letter in full, it is clear that when he says he expects and hopes to pay more taxes, it is because he expects and hopes that profits will increase.
But doesn't that go both ways? It's a bad path if you are only allowed to post your thoughts on Twitter if you put forward exactly the right (according to you) political or social views publicly.
The owner of a GPL project doesn't own the copyright for contributed code (and therefore can't license it themselves under GPL), unless they receive a copyright assignment.
It's authoritative though less than comprehensive, and more (though, unless I'm conflating it with something else, not entirely) focussed on physical health.
Credit card rates with your own merchant account are 3% - 8%, depending on your industry and chargeback history.
Federal Marginal tax rates are 10% - 38%, plus maybe 5% in MN.
If they are giving you a 5% - 10% discount for cash, sure, it's probably because they appreciate skipping the credit card. If they give you a larger discount for paying in cash, they probably aren't reporting the income.
For card-present goods and services it's likely lower, but for card-not-present online software sales from a small company, rates with your own merchant account can be even higher than 8%. This is a big advantage of using Stripe and the like.
"WinRT" XAML runs great on Windows 8+ and is mostly forward compatible with UWP XAML (especially 8.1+ universal XAML). (Though statistically "everybody" that was on 8 is now on 10. It's 7 that will be the next XP.)
Windows 7 is the outlier, but this isn't that much of a different argument from the complaints that Windows XP had terrible out-of-the-box support for WPF. The same arguments stopping people from using UWP today seem very deja vu to the arguments against WPF even back when in Windows 7.
UWP XAML isn't even that different from WPF XAML. I've got a feeling for some LOB applications maintaining a UWP and WPF build side-by-side is relatively straightforward (and definitely more straightforward than those of us that for various reasons worked on side-by-side XAML builds for WPF and Silverlight).