> It cost at the very least the salary of a software engineer, though most likely a lot more. Autodesk is not some passion project of a group of volunteers who just want to keep it up.

It's not a passion project, and that's why I find it very unlikely that they are not using some off-the-shelf forum software. I doubt Autodesk would be paying anything near a full software engineer salary for anyone working on the forum. Of course there will be some developer integrating the forum with the rest of their website, but that is hardly a full-time job. Moderation is probably also not done by engineers but by support staff that doesn't receive a salary at the level of an engineer.