Are you saying they are using Lithium which is closed source? Jive and Lithium are enterprise level platforms which have enterprise level complexities in implementation and cost which is not warranted for a small community forum. Even then Lithium has a starting price at $50k not $1.5m.
But what relevance does that have to anything I said? Yes most of these companies are using Lithium. Yes, Lithium is closed source. Yes, they are using this platform because of the extensive capabilities and massive feature list.
You say it's not warranted for a small community forum, you're correct. Yet, this is no small community forum, in fact, it's in the top 25 forums in the world right now in terms of user activity. Probably much higher than that even.
Notice my reply was directed at the quote by "hilariousandco" which stated that he thinks that possibly in the future businesses who require these massive sites for their support infrastructure will turn to open source software. I was merely stating that isn't likely to be the case because no open source software is ever going to come close to what a licensed software can do.