There was a shakedown letter from a lawyer with the threat of a lawsuit, it seemed like they hoped people would just pay some money but they couldn't even put any effort into responding to enquiries.
Unless and until someone is served papers, there isn't any lawsuit.
The lawsuit can be filed but not served, so technically, a lawsuit could exist. But until the service of process happens, effectively there is no lawsuit, as the service is necessary for the court to obtain jurisdiction over the defendants. Additionally, serving the defendants in this situation is not as simple as hiring a process server to serve them. It will require lawyers (and payment of lawyer fees) in every country where a defendant resides, as well as a thorough analysis of treaties that may exist between the countries governing the exercise of jurisdiction by Croatian courts in the other countries as well as an analysis of the relevant laws in of each of the countries where a defendant resides. This would be a very expensive feat to pull off, and based on the publicly available financial statements relating to his business that I was able to observe online, I don't believe that he has anywhere near the financial resources necessary to pull that off.
I have no knowledge whatsoever of Croatian law, but I doubt that Croatian courts will allow a lawsuit to sit without being served. There is likely a time limit on service that will result in dismissal of the lawsuit if the papers are not served within the required time.