@akumbhare They do it the same, they've just started with v0.X.X while in active development. Eventually, there will probably be a a 1.X.X, etc.
They are currently using 0.minor.patch, and haven't had a major release yet.
You can use stable branch in production if you want (I think this forum uses the stable branch), it is based off of the master branch, so isn't actually guaranteed stable, I think.
Use branch v0.6.x in production, but, be aware, this forum software is still under active development, isn't feature complete, and there will be breaking changes down the line (but updates are pretty easy).