I am wondering nobody is thinking about using plain HTTP-Requests to consume RESTful webservices. I didn't try it but for me it feals like a much more elegant solution.
Powerbuilder GET request with request headers - Stack Overflow
It's a bit more to code in PB because you need a JSON parser, but I really would avoid using Powerbuilder .NET.
If you would like to use a wrapper, try C# and reduce dependencies.