Bolt Launcher comes with a built-in plugin loader for RS3. Using the plugin loader is optional and can be enabled in the settings menu.
Bolt is third-party software and is not affiliated with RuneScape or Jagex.
Yes. The plugin loader doesn't break the game's terms of service.
Yes, very sure. It doesn't do anything that isn't also done by well-known harmless software like OBS, Alt-1, and various gaming overlays like Discord, Steam, NVIDIA ShadowPlay, and so on.
Due to RS3's strict terms of service, the only things Bolt is allowed to act on are the things it can visually see on the screen. It does this by inspecting graphical information as it gets sent from the CPU to the GPU. It's not allowed to inspect or modify the game client or cache files, which means it's not as powerful as old school's RuneLite. The main thing it's extremely good at is detecting images and textures on your screen, even if they're scaled, rotated, coloured, transparent, partially obscured, or part of a 3D object.
Bolt plugins are decentralised. That means there's no single central place where you can find them, and you can only install them by being given the URL to a plugin that someone has made. There are no official plugins. Find useful plugins by asking the community.
A plugin loader and a plugin are two different things. Having a plugin loader installed doesn't necessarily mean you have any plugins installed. There are no official or pre-installed plugins. You're free to install only the ones you want to use.
Anyone. I have no control over (and accept no responsibility for) what anyone does with Bolt. Anyone can make any plugin at any time and publish it for anyone else to install. I'm not an authority in that process and nor is anyone else.
See the documentation.