If the court ruled that the work is not creative or unique enough to qualify for copyright protection, then why does it matter that the work was not registered with a copyright office? The implication of this would be that foreign artists would have more legal protection and rights in Luxembourg than Luxembourgers.
It's also fairly possible to demonstrate that it's a derivative work and that the artist would have had to have used the photo as a reference because the painting is a 1:1 reproduction of the photo, it's actually impressive how well it's reproduced. Flashing image warning: https://i.imgur.com/RERFdBZ.gif
As a nitpick, in this post you're saying it's a derived work but in a child comment you're saying it's a transformative work so it's not 'pure copyright infringement'. In pretty much every country, producing a painting using a reference photo is derivative and is 100% covered by copyright law to the point that it's the example legal scholars use to demonstrate what a derivative work is. It cannot be the case that the photographer can sue for revenue on the painting without it being a copyright violation because that's the legal mechanism for which the photographer has any rights to sue the painter. However that's not the case here, because the court ruled that the photographer has no rights or protection under copyright law because the photo was found to lack the creativity or uniqueness to be afforded protections by copyright law.
As far as 'transformative' goes, it's not a concept that exists in my European countries legislation, but it's a term legal scholars use to demonstrate when a derivative work can be considered fair use using vaguely defined terms such as whether the work substantially changes the 'meaning', 'emotion', or 'aesthetic' of a work, and examples of this are things like reviews or criticism of a work (e.g., movie) or things like a parody. Merely reproducing a photograph is not considered transformative enough to be considered fair use, and even making substantial changes to the photograph may not make it transformative enough to be considered fair use, much like taking a photo of an artwork is not transformative, producing a movie from a book is not transformative, transcribing music is not transformative, etc.
4chan has rules, albeit incredibly lax and with biased enforcement, but they are enforced (see /bans) eventually. Many of the larger boards seem perpetually and woefully understaffed which gives the impression that it's a lawless website to a casual observer, but depending on the time of day it's likely just the case that there's an insufficient amount of jannies to deal with the volume of posts, with posts being deleted upwards of an hour after being posted.
One of the more notable examples of rules being enforced on 4chan was its stance and subsequent banning of anything relating to Gamergate, causing a large part of the community to leave for 8chan. Or more recently the removal of the /qa/ board for cross board raiding.
It's also fairly possible to demonstrate that it's a derivative work and that the artist would have had to have used the photo as a reference because the painting is a 1:1 reproduction of the photo, it's actually impressive how well it's reproduced. Flashing image warning: https://i.imgur.com/RERFdBZ.gif
As a nitpick, in this post you're saying it's a derived work but in a child comment you're saying it's a transformative work so it's not 'pure copyright infringement'. In pretty much every country, producing a painting using a reference photo is derivative and is 100% covered by copyright law to the point that it's the example legal scholars use to demonstrate what a derivative work is. It cannot be the case that the photographer can sue for revenue on the painting without it being a copyright violation because that's the legal mechanism for which the photographer has any rights to sue the painter. However that's not the case here, because the court ruled that the photographer has no rights or protection under copyright law because the photo was found to lack the creativity or uniqueness to be afforded protections by copyright law.
As far as 'transformative' goes, it's not a concept that exists in my European countries legislation, but it's a term legal scholars use to demonstrate when a derivative work can be considered fair use using vaguely defined terms such as whether the work substantially changes the 'meaning', 'emotion', or 'aesthetic' of a work, and examples of this are things like reviews or criticism of a work (e.g., movie) or things like a parody. Merely reproducing a photograph is not considered transformative enough to be considered fair use, and even making substantial changes to the photograph may not make it transformative enough to be considered fair use, much like taking a photo of an artwork is not transformative, producing a movie from a book is not transformative, transcribing music is not transformative, etc.