Hi Konstantin,
You can develop 4 types of technologies you can use for PowerBuilder projects:
1. Traditional Client/Server
This is the traditional project type that has been in all versions of PowerBuilder. Language is PowerScript and IDE is PowerBuilder.
2. PowerClient
This is simply a deployment method for traditional client/server. Using this project type it will create automatic installer/updater. Language is PowerScript and IDE is PowerBuilder. Here is more information about this option: https://www.appeon.com/products/power-client
3. PowerServer
This is a special cloud compiler for the PowerBuilder IDE. It recompiles any PowerBuilder project (even though originally project was client/server) to cloud-native architecture. Language is PowerScript and IDE is PowerBuilder; however, to add user authentication to the generated Web APIs you will need to do a little bit of C# coding. Here is more information about this option: https://www.appeon.com/products/powerserver-tour
4. .NET DataStore
You can develop REST APIs with DataWindow technology. It is technically possible to use the .NET DataStore to just create a non-visual library, but most common use case we target this for is REST APIs that can be consumed by any client (including traditional client/server, PowerClient, and PowerServer). Language is C# and IDE is SnapDevelop. Here is more information about this option: https://www.appeon.com/products/powerbuilder/dotnet-datastore-rest-apis
Best regards,
Armeen