[rodneyzeng]

They did not exclude possible charge for major upgrade.

I am not relying on typora. I use it for WYSIWYG markdown editing with equations. Actually I like more the functionality to copy pasted image to a folder - that is the only feature I really like.

I still have not convinced myself to pay for it.

[sigzero]

You should ask them then. I find that "one-time payment" is pretty specific. Still, $15 is absurdly cheap for what you get.