Connect to Magento 2 Composer repo and list packages you can access

pkglist.php

<?php


/**
 * Return the path of the auth.json file.
 */
function findAuthJson() {

    // Windows sets HOMEDRIVE and HOMEPATH, but cygwin sets HOME.
    if (!isset($_SERVER["HOME"]) && isset($_SERVER["HOMEDRIVE"])) {
        $home = $_SERVER["HOMEDRIVE"] . $_SERVER["HOMEPATH"];
    } else {
        $home = getenv("HOME");
    }

    $paths = [
        $home . '/.composer/auth.json',
        'auth.json',
        'app/etc/composer/auth.json'
    ];

    foreach ($paths as $path) {
        if (file_exists($path)) {
            return $path;
        }
    }

    echo "Unable to find 'auth.json' file holding composer repo keys\n";
    exit(1);
}


/**
 * Returns username and password from ~/.composer/auth.json.
 * Returned in assciation with keys "username" and "password".
 */
function getAuthUsernamePassword() {
    $authName = findAuthJson();
    $auth = json_decode(file_get_contents($authName), true);
    $up = $auth["http-basic"]["repo.magento.com"];
    return $up;
}


/**
 * Fetch packages.json file.
 */
function getPackagesJson() {

    $userpass = getAuthUsernamePassword();

    $process = curl_init();
    curl_setopt($process, CURLOPT_URL, 'https://repo.magento.com/packages.json');
    curl_setopt($process, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
    curl_setopt($process, CURLOPT_USERPWD, $userpass['username'] . ":" . $userpass['password']);
    curl_setopt($process, CURLOPT_TIMEOUT, 30);
    curl_setopt($process, CURLOPT_RETURNTRANSFER, TRUE);
    $return = curl_exec($process);
    curl_close($process);

    return json_decode($return, true);
}



$packagesJson = getPackagesJson();

foreach ($packagesJson['packages'] as $packageName => $versions) {
    $keep = false;
    foreach ($versions as $version => $package) {
        $description = $package['description'];
        $type = $package['type'];
        if ($type !== 'magento2-module'
        && $type !== 'magento2-library'
        && $type !== 'magento2-component'
        && $type !== 'library') {
            $keep = true;
        } else if (substr($packageName, 0, 8) !== "magento/") {
            $keep = true;
        }
    }

    if ($keep) {
        $versionNumbers = implode(' ', array_keys($versions));
        echo "$packageName [$type]\n";
        foreach ($versions as $version => $package) {
            $dep = '';
            if (isset($package['require'])) {
                foreach ($package['require'] as $dp => $dv) {
                    if ($dp !== 'php' && $dp !== 'composer/composer') {
                        $dep .= " $dp:$dv";
                    }
                }
            }
            $line = "    $version$dep";
            if (strlen($line) > 78) {
                $line = substr($line, 0, 75) . '...';
            }
            echo "$line\n";
        }
        $d = wordwrap($description, 72, "\n    ");
        echo "    $d\n\n";
    }
}

For future searchers, this information can now be found within the My Purchases section of Magento Marketplace.

It is listed as the "Component name" in the Technical details popover that appears below the Download button for each module.