The JVM automatically chooses whether or not your GPU is used or not. If your GPU is used, it's sole purpose is to save CPU processing power. The only process within OSBot which makes use of the GPU is when we copy image buffers around to render the canvas and loading screen which you've screenshotted. OSBot requires double-buffering on every client and this may lead to your GPUs powering up. Double-buffering allows us to render graphics on-top of the RuneScape canvas in a synchronized fashion. An external card wont benefit you in any way because onboard graphics (see Intel processors) would handle this the same way.
Check background and other processes running.