Do you think a group of NU developers are allowed to publish such a website without some kind of authorisation from NU?
As far as I know, yes. NU does not limit its members from innovating, especially in the realm of technology. The rules of this organization (imo) are quite flexible and tolerant so that the organization's logo can be displayed anywhere without the approval of the relevant authorities if it is only to show that the main people involved are (provably) members of the organization. This is an effort to get higher exposure, especially as you said, this is a social organization with the most members.
I remember one application "NU cash" which on its journey, used such a method until it was finally officially launched[1]. There was also the "NU Tangerang" app[2] which was developed with the aim of local scale use, this is similar to Nunomics in terms of vision (cmiiw).
1. https://www.nu.or.id/nasional/nucash-dompet-digital-santri-resmi-diluncurkan-wGUhj
2. https://mediaindonesia.com/teknologi/442374/sambut-hari-santri-nasional-mobilecom-luncurkan-aplikasi-nu-tangerang
How is it possible that you are here since 2018 and I never laid my eyes on you

+1 karma
There are 2 reasons why I think Nunomics is not just a group of developers but rather NU is involved.
1) Nunomics doesn't simply allow gold trading, it allows buying/selling physical gold (fisik emas, the only two words I know in Indonesian).
For that you need a vault - approved by the Indonesian government; you need permits, a broker able to buy and sell fisik emas on international gold markets - the nearest one for Indonesia is Singapore; a company for logistics; I see the Jakarta Futures Exchange mentioned on Nunomics, that means there must be already a partnership with the JFX... etc.
In order for this app to be put to work you need all of this, and more.
How many companies are there in Indonesia capable to do this? How many potential customers are there for such an app? Basically zero.
A group of developers spending 6-12 months of their life building and launching an app which hasn't nor will have in the foreseeable future any chance of being used?
2) There was already the official launch of
Pospay Gold with the participation of Wakil Presiden (Wapres) K.H. Ma’ruf Amin.
There is a reason why you can see the kinesis logo on that video.
Here is the official statement
Luncurkan Pospay Gold, Wapres Dorong Penguatan Pengembangan Ekosistem If you note there are similarities between PosPay Gold and Nunomics - basically - as far as I can understand - the offer the same service.
So, given that Kinesis has a long standing partnership with the Indonesian government, and that they have already mentioned in the past that they were working with NU, I tend to think that it is as kinesis announcement says, Nunomics is not just a group of developers but the result of a partnership between Kinesis and NU.