It's not an active account if by "active" they mean "generating content". While Twitter isn't a typical content aggreagation site like Youtube or Reddit, tweets are still "content" in the sense that they drive further user engagement on the site.
Words used to mean things. The current HN submission title just says active, heavily implying accounts with any kind of activity (eg. like, follow/unfollow), not "users who Tweet".
Sure, clickbait headlines are the norm and the devil lurks in the details, but still, many comments have been spent on this, because it's clearly misleading.
~80% of email is spam, it doesn't surprise anyone, because it's so cheap to send spam. Similarly it's easy to create fake accounts and spam, yet it doesn't mean much.
Who's counted as "engaged"? The people reading, or only the people writing? More to the point, if Twitter moved to a subscription model, would zero lurkers buy in?
Seems like social network aren't interested in counting those that don't use all potential features of the platform. I'd say a lurker/ghost member is definitely an active account.
I would say that if someone is able to be advertised to (since that is what makes the business money) then they should be counted. So yes, there should be no requirement to tweet to be counted.
"Active user" is a common industry term with a well-defined meaning. It's misleading to use it to mean something else, particularly when there are a number of more appropriate choices, e.g. "20% of Twitter posters".
The article clearly defines those accounts as "active" because it's the only way an external observer can somehow isolate an "active" group. Only twitter can know how many users are "lurkers".
And since they are trying most probably to get some PR for their company, they use their specific definition of "active Twitter account".