Not sure if it is legal or not but it is very old. Given it is a few versions behind I would say you advised correctly to stay away from it. My guess would be not an authorized reseller.
If yes, will this software be supported?
you can still download the old patches but thats about it because Windows xp is long dead
I would aviod it anyway, legal or not
Captivate 7 is five years and four versions old.
Captivate 2017 is Au$1815 for a full licence (My browsers redirect to Adobe Australia)
Google tells be that €1055 works out to A$1626, so a saving of less than $200 for a very out of date product. If it is dodgy, then you have to admire their cheek in expecting people to pay nearly the price of the current version.
Did they have any other special offers advertised on this website?
She asked me about this old version because she uses an old Windows 7 PC.
So I advice her that a new "standard" Windows 10 PC is about 500/600€, and that the latest Captivate is 35,99€/month (on the French Adobe site).
It's therefore cheaper and it will take years to reach the price of this old version, unsupported and without future.
So she was pretty much okay.
PS for Adobe Team:
What about the MacOS version of Captivate?
Sorry. No question.
I missed the existence of the Mac version.