The code for the backend can be found here: https://github.com/genome-nexus/genome-nexus.
Genome Nexus provides a REST API for variant annotation. See API
Clients in various languages can be generated to access it. See API
Genome Nexus Website
The frontend of the website is here: https://github.com/genome-nexus/genome-nexus-frontend.
The main consumer of the Genome Nexus REST API is cBioPortal. cBioPortal provides visualization, analysis, and download of large-scale cancer genomics data sets. Variants in cBioPortal are annotated using Genome Nexus. The other examples in the figure are potential other consumers. See also: Tools
Command Line Interface
There is a command line tool to annotate MAF and VCF files, see API