Yes. HEXOstudios has no network access of its own, no account and no cloud. It works with your files where they already are and never copies them into itself, and HEXOforge converts on your Mac. Only the Mac App Store talks to Apple, for your download, trial and purchase.
Your files
You choose which files and folders HEXOstudios can open. It works with them where they are and never copies them into itself. So that your library can reopen them after a restart, HEXOstudios saves a macOS access permission for each location you choose.