(1) I am not sure I understand the question. It seems to me that it really boils down to "Do you trust the browser to run arbitrary code?" There is truly no way

(1) I am not sure I understand the question. It seems to me that it really boils down to "Do you trust the browser to run arbitrary code?" There is truly no way for CheerpX to do anything more than what your average Web page could do. (2) We are implementing syscalls and devices as they are needed for the various use cases we are considering. In general even if something is not natively supported in the browser it can still be virtualized to various degrees. In particular CheerpX provides a virtualized FileSystem that does not map to your local files. The same would apply for the virtual disks in traditional VMs though. (3) We plan to release benchmarks soon, but the level of performance is very promising. Consider that we have been using the Flash plugin as our main benchmark which is very demanding. For the REPL use case the limiting factor right now is I/O performance, but we are already working on this and we thing we will achieve much better results very soon. In general, all aspects of CheerpX performance will improve, we are really not done yet.