It sure is, and fully open source. https://www.altis-dxp.com/ (https://www.altis-dxp.com/resources/docs/getting-started/#cr... to jump straight to the download from Composer stuff; https://github.com/humanmade/altis for the repo)
The pre-approved plugin list (https://www.altis-dxp.com/resources/pre-approved-plugins/) returns 404 though :(