No one can support .rh format, except RH/SAP. It is a closed, proprietary format. And forget about html5, canvas, webgl etc. These are too open, SAP / RH have traditionally created data silos rather than working off of open standards.
SAP VEV , formerly DeepView, does have a complete JS interface. The viewer doesn't have to be a popup. Look in the docs, you can embed the viewer in a page, and disable all the menus etc through appropriate javascript calls. The docs are distributed with the viewer sdk, however it is getting rather hard to come by now. Also helpful, and included with the docs, are examples.