Not only can you install the black box on the Server, but also the whole Client software which is then downloaded by ClickOnce as soon as a customer starts using it.
The way it works is the following:
For all this to work, the client application has to be written in C#. The black box is an APL+Win application which remains on the Server and runs on the Server; the client app is a C# app which resides on the Server but does not run on the Server: instead it is quickly downloaded from the Server each time a customer requests it and starts automatically on the client computer.
Note that the Server application could indeed be (DEMO.W3+ProCash.W3) and (DEMO.W3+LANDEV.W3): in that case, we could use everything that you have already written in APL. We would just need to build a front end in C# which would be the client application.
Or the Server application could be just ProCash or LANDEV, but in that case we would need to convert DEMO.W3 to C# and build an interface around it. So this would be more work but could also be done.
All this, of course, requires that APL+Win be installed on the Server and that you have full access with Administrative rights to the Server.
If you encounter any difficulty in getting those rights to access a Server, there is always the possibility on installing everything on my Internet Server. I would then give you an FTP account allowing you to install your software and update it, etc. And I would create the environment that would allow all this to work fine.
I have written several Client-Server C#+APL+Win application this way and converted several other APL+Win customer applications using this technology. It works beautifully and very efficiently.
The nice thing about working with a Server in a Client-Server mode, is that , when you need to update your application, you just need to upload new files to the Server, and suddenly ALL your customers, everywhere in the world, get the new version of your application without you having to do anything else.