Free GoJS Alternatives
The best free alternative to GoJS is mxGraph, which is also Open Source. If that doesn't suit you, our users have ranked eight alternatives to GoJS and five of them is free so hopefully you can find a suitable replacement. Other interesting free alternatives to GoJS are Diagram-JS, Draw2D, JavaScript InfoVis Toolkit and jsPlumb.
mxGraph is an interactive JavaScript HTML 5 diagramming library. It can be used to build anything from simple workflow editors, up to fully functionality online diagramming applications, like diagrams.net.
Discontinued
Mxgraph was discontinued, but some forks are listed in the description of the GitHub repository.
mxGraph vs GoJS opinions
DeuchnordmxGraph is too low level compared to GoJS
Diagram-JS is an open-source toolbox for displaying and modifying diagrams on the web.
Create Visio like drawings, diagrams or an workflow editor with the Draw2D Javascript library.The User interface allows interactive drawing by using your standard browser. No additional software; no third party plug ins. Just run it and use it.
Discontinued
No releases in almost a year:https://github.com/freegroup/draw2d/releases
JavaScript InfoVis Toolkit is a JavaScript library for visualizations and diagrams. The JavaScript InfoVis Toolkit provides tools for creating Interactive Data Visualizations for the Web.
Built on the open source project jsPlumb, the Toolkit unifies several years of experience of what you need to build applications fast. Concentrate only on what makes your application unique.