Singularity/Apptainer is a free and open-source container platform that allows users to build and run containers on high performance computing resources.
SingularityCE is the community edition of Singularity maintained by Sylabs, a company that also offers commercial Singularity products and services.
Apptainer is a fork of Singularity, maintained by the Linux foundation, a community of developers and users who are passionate about open source software.