#10 Agreed, any JS engine is bound to be obsolete since JS is a terrible language for application development.
#5 What about JavaFX? (Admittedly, I can't find any other chess site which uses JavaFX so there isn't a good example to copy.) It offers all the same security guarantees as Java Web Start (that binaries are securely downloaded) and it's capable of manipulating the DOM. However, it has the same risk and challenge any client-side software has: in order to run on the client machine, it's necessary to download and run the browser plugin.
#5 What about JavaFX? (Admittedly, I can't find any other chess site which uses JavaFX so there isn't a good example to copy.) It offers all the same security guarantees as Java Web Start (that binaries are securely downloaded) and it's capable of manipulating the DOM. However, it has the same risk and challenge any client-side software has: in order to run on the client machine, it's necessary to download and run the browser plugin.