The main server is Node; this one is Java, because that is what the underlying content needs. Keeping them separate means neither drags the other's runtime along, and you install only the half you need. Trading partner agreements are also the part of B2B integration that is genuinely fiddly to inspect by hand, which makes it a sensible thing to be able to ask about. Same experimental caveat as its sibling.
A companion server covering Trading Partner Management in SAP Integration Suite — the agreements and partner profiles that B2B exchange runs on. Also labelled experimental.
Access to trading partner management content, which the author's main Integration Suite server does not cover.
Java and Gradle at the versions the README names; built from source. The author recommends running it beside their Integration Suite server.