To build riak, Erlang OTP 22 or higher is required.
make rel will build a release which can be run via rel/riak/bin/riak start. Riak is primarily configured via rel/riak/etc/riak.conf
To make a package, install appropriate build tools for your operating system and run make package.
To create a local multi-node build environment use make devclean; make devrel.
To test Riak use Riak Test.
Up to date documentation is not available, but work on documentation is ongoing and the core information available in the legacy documentation is still generally relevant.
Issues and PRs can be tracked via Riak Github or Riak KV Github.