Discourse (www.discourse.org) is discussion forum software, 100% open source (GitHub repo) and with many contributors, more features than Talkyard (see comparison below), more integrations, and a plugin ecosystem. It has better support and uptime guarantees than Talkyard. A bigger company, less risky.
Talkyard works better for larger discussions. That's because it's threaded, so when people start talking about slightly different things in the same main discussion, they still don't interfere with each other.
Talkyard is also, we think, better for discussing ideas and making decisions together: You can sort comments so the more insightful ones appear first (rather than the oldest ones). Then, everyone gets a better understanding of reasons for and against.
Likewise, with Question-Answers: In Talkyard, the good answers surface to the top; they're the first you'll see.
There are also partly implemented anti-cognitive biases features that deal with things like group think, anchoring bias, appeal-to-authority. (This builds upon anonymous posts done "the right way" .)
Discourse can be, on the other hand, simpler to use, since it's flat (not threaded).
Both Discourse and Talkyard have chat channels, but Talkyard's chat is still mostly unimplemented. Discourse has a nice sidebar where you can add custom links. Talkyard lets admins reconfigure everyone in a group, by editing the group — which is nice, if there're say 100 group members.
An analogy: You could say that Talkyard is more like having a subreddit or StackOverflow community at your website, while Discourse is more like having a thoughtful and slow paced chat at your website. Anon-posts-in-a-good-way could be a whole blog post, in itself.
Price and Hosting
If on-premise. SaaS always auto upgrades.Yes
Users groups & Permissions
Configure everyone in a group at the same time, e.g. subscribe them to a category.€5/c$50
Post a question to a user group, without knowing who is the best person to ask.€5/c$50
Grant read and write permissions on categories to user groups.€3/c$50
Discussions & Content
Q&A and Knowledge Base
So you won't judge an idea based on who posted it.€3/c$300 but risky