Does that mean that it's final? Could they attempt to revive it again, or does it seem they did try (by amending) but did not succeed in persuading the examiner? I'd love to know if it's 'safe' to pursue my idea in light of the above, or if there is still something they may be able to do.
Smart thinking.
From your description it seems you're reading down the file's "Transaction History" of events rather than viewing the actual documents. On the "Image File Wrapper" tab you can pull PDFs of the actual correspondence. Read the Notice of Abandonment and any documents associated with it (same time frame, especially any "Interview" summaries) to see if there is any comment from the Examiner to the effect that s/he called the applicant asking if they intended to allow it to go abandoned.
Many Examiners do this just prior to issuing the abandonment notice. If there is a statement on the record to the effect that the applicant told the Examiner they
did intend to allow it to go abandoned, then this simplifies things for you considerably.
The reason is - exactly as you asked - an applicant is permitted to pay fees and revive an abandoned application. But only under 2 circumstances - (1) where the abandonment was "unavoidable" (very difficult to prove), and (2) where the abandonment was "unintentional" ("oops, I just screwed up, I didn't mean it, let me pay you a hefty fine and get it back on track").
But if the applicant or applicant's agent told the Examiner they
intended to abandon it is extremely difficult to argue later that either revival scheme can be valid.
If no such statement is present in the record, you have less certainty. An applicant can in good faith make a mistake and correct that mistake later. The petitions office often applies a "reasonableness" standard when deciding to grant or deny a petition to revive, and the analysis is always very fact-specific. But as more time goes by, the less reasonable it becomes to argue one didn't intend to abandon. Unfortunately there's no bright line rule here. I've seen pro se inventors get their application revived even 2+ years after the abandonment. And I've seen corporations with in-house legal have petitions denied after just 6 months delay.
Sorry there's not a better answer here but this is an issue for all of us who have to advise businesses, which is why I love it if the Examiner writes a phone interview summary saying the applicant intends to abandon.
One thing you can say with certainty no matter what you find in the file wrapper is that if the only relevant patent application you know of went abandoned 9 months ago, then if you decide to proceed, you are clearly proceeding in good faith that you are not infringing anyone's rights.
Last thought - EVEN IF they told the Examiner they intended to abandon, I'd try to find out if they filed what is called a continuation ("child") application. This filing can be done at any time prior to actual abandonment of the case you are looking at. Back on the PAIR record, look for a tab called "Continuity Data". These data run backward to any "parent" applications (preceding the application you're looking at) and forward to any "child" applications such as a continuation or divisional application filed from the application you're looking at.
Any child application should normally have published within about 6 months of filing (i.e., not much more than about 6 months after the parent abandoned), so if a child application exists, it should be linked under the Continuity Data tab. If the Continuity Data tab is missing that means no related applications are filed. (Or - and I think this would be very rare but just to cover the bases - none that are public information. In yet another twist (sorry!), I believe an applicant can file a "non-publication" request even for a child of a published parent. Although I have not heard of this actually occurring.)