They use Discourse. It's built (and probably still led) by Jeff Atwood, who's known for ~~building~~founding StackOverflow with Joel Splosky. Here's the announcement post when discourse was launched He still blogs about the design and code decisions they made regarding the software, which is how I discovered it.
Since it's in active Open source development, you can go to the Discourse Discourse (heh) and suggest improvements and such.
You might consider looking at Trello (https://trello.com/). It's like an online roadmap platform but also gives follows/backers the oppertunity to vote for features they would like to give priority to.
Stonehearth uses it too, their page is at https://trello.com/b/4XvM0SUd/stonehearth-community-roadmap to give you an idea of what it looks like.
A good source for weather is this: https://weatherspark.com It brings typical weather not live weather. In this case they can bring average per season for each location, including wind speeds and add fake variation per day.
According to their feature trello they are pretty far with remote stands. I wouldn't be surprised if they got something to show in the next devblog or can even push something playable on the experimental branch next month.
With multiple floors we probably have to wait until after their summer break though. Which is fine with me, I think they deserve a break :)