Martin,
The .NET code is just a wrapper around the Platform SDK resources which can be called from any language. If you do a Google search on the following:
docuware platform "non-.net"
you will find several posts about that. More recently, DocuWare has even released a Postman collection of examples that illustrate how to perform calls to the Platform SDK from any web-capable language or scripting tool (e.g.
curl):
https://developer.docuware.com/rest/examples/postman-collection-download.html
There is also a link to some node.js examples there which may translate more easily into JavaScript...
Good luck!
Joe Kaufman