Two ways - First is to join 2 meeting a year, although sadly we haven't had a meeting since pandemic stuff. Will have some later in the year though, but nothing setup yet.
Other way is to pay the $24 yearly membership fee. You will need to go to our main site (can't do it in the app) and on the front page there is a widget in the top right corner of the page with a dropdown to choose your membership level. It will then direct to paypal for the fee.
No idea either. It may have been built by someone or something, but not really sure as it was around long before my time here. Although we have had members test it against some name brand one, both expensive and cheap meters, and surprisingly they all came up with the exact same readings. So we are pretty confident in its accuracy at least.