The URL for this website provided in those answers is: http://uniquation.com/ If you try it, you can see that the link no longer works (you only get the information that this domain is for sale)
Question 1: Does somebody know whether this search engine no longer exists, or it was just moved to another domain?
Question 2: Is the source code available somewhere - so that somebody could try to run the same engine on their own hosting (at least in theory)?
Question 3: Does somebody has enough experience with uniquation (back when it used to work) to be able to say how the results compare to some other similar search engines? (For example, the ones mentioned here: How to search the internet for strings that consist mostly of math notation?)
1There are also some comments on main and on meta which mention this site. Searching in the post with this link in the whole network, I found also this post on MathOverflow Meta: Is there any third party search engine for MathOverflow? And this post on TeX Stack Exchange: What useful web services are out there?
2You can see how this website looked in the Wayback Machine. In fact, it seems that the snapshots of the search results for some searches were saved too - after I clicked on the first link in that snapshot, I got search results for $\sin(\alpha+\beta)$