I have worked in IT for many years now and this appears to be just another way of sharing files (legal and illegal). The problem with this that I see is it is a way of opening up your system to the outside world to store or retrieve files from your system without you even knowing who is storing or accessing the information. Anytime you open up ports on your computer to the outside world, you are inviting someone to hack into your system. I do not want you to be paranoid about opening ports on your system, but that you should know what the hazards are of opening up such ports. It appears that it is running a web server for others to access your system, and as a system administrator we have to patch the web server whenever there is a potential compromise found in the software, and happens quite often. The problem is you put the software on and forget it, and if a compromise is found in the software whoever has the software on there system is a potential target to get hacked into if it has not been patched or even if a patch exists!
You have mentioned Darknet mode. It is still using a port on your computer to communicate with other users and if "someone in charge" wanted to shut it down it would be very easy. All they would have to do is to filter out that range of ports to cut it off. Result is no communication in that range. I have had to do this on our network to keep people from running there own software and compromising our network. Please be very careful with this kind of software!
Another thought is you do not know the creator of this software and it is free. People do want to get paid for there work and a lot of times this kind of thing may cost you more in the end! There is no way of knowing if the software has some malicious code or spyware included in it!
Sorry for being a downer on this but thought it was important that you make sure of what you are doing and prepared to maintain the software and deal with hackers. The good ones are very hard to find and the best you will probably never find!
Be careful and keep looking up!
With love Dave