The download page has some problems.
1) none of the links for the archetypes work
2) links to hashes and sigs should use https
3) the gpg command to verify sigs is incomplete; it needs to be
gpg –verify isis-1.13.2-source-release.zip.asc isis-1.13.2-source-release.zip
i.e. both the sig and the binary file are needed.