What does "unmaintained" mean for a resource?

[ForestForTrees]

There is an addon that I'd like to use, but it is marked as unmaintained. Someone listed the Addon, Back to the Top, by MattW, as one of their favorite addons on Monday, though:
https://xenforo.com/community/threads/favorite-xenforo-add-ons.110234/#post-1023340

What does "unmaintained" mean? In other words, how is it determined when the tag is added or removed from a resource?

Don't read the following. Seriously, you'll never get 30 seconds back:

I wish that it was easier to find this piece of information. Were this my site, I'd edit a template so that there was a link from the resource manager to a FAQ that gave first a simple explanation of how something is marked as unmaintained. OTOH, I suppose that they might not want to edit templates given that this is the demonstration forum. Alternatively, it could be a sticky in the Add-on Releases subforum. (Either way, I'm glad that this company is still the opposite of a Dilbert cartoon in that the engineers seem to have a lot of influence. Staff seem to respect rational argumentation and Chris has a brilliant mind for making people feel communicated with. People make fun of the phrase "safe space," but this is a safe space to respectfully and professionally express a concern. Thanks for that.)​

Anyhoo, back to the topic at hand. What does unmaintained mean?

 

[Chris D]

The "Unmaintained" prefix is added by resource authors to indicate that they are no longer actively maintaining their resource.

We will add the prefix on their behalf should an author be inactive for a considerable amount of time, or if the external purchase URL no longer works.

 

[ForestForTrees]

Thanks!

I searched the support thread for "unmaintained" using "Search this thread only" and found no occurrence of the string. I guess the next step is to post in the relevant thread to ask what is up?