You need a ChatGPT account, and a free one works. OpenAI's announcement lists Images 2.6, GIFs included, across all subscription tiers on web, mobile, and desktop. We verified both flows on a Free plan account on announcement day.
Nothing to install. The web app at chatgpt.com is all you need.
Images and GIFs use your ChatGPT plan's image allowance, and OpenAI doesn't publish exact numbers for the free plan. We generated one GIF and one image on a Free account without hitting a cap or an upgrade prompt.