What platform does Atlassian use to build its community? Is it fully custom-built?

Question

I think the Atlassian Dev Community is built using Discourse if I'm not mistaken. What about this community?

Szechuan Sauce · Answer

From a regular forum member's perspective, discourse is the best forum software I've used. If Team Atlassian ever consider moving this community over to discourse, I'm all for it. Just saying. :p

Davin Studer · Answer

This community is built on Kohros, which used to be called Lithium.