You can download a zip file from the releases page. Please see the DeepSEA language reference for installation and usage instructions.
The zip file includes pre-built binaries for Linux (Ubuntu) and MacOS. Since they use some system libraries, it is possible that they will not work on every version of Linux or MacOS. It is also easy to build the binaries from source yourself, following the instructions in the src directory.
The DeepSEA compiler includes files taken and modified from CompCert, so it is developed pursuant to the CompCert licence. In particular, it may only be used for educational, research, personal or evaluation purposes, and not for commercial use.