Can you just create a simple PHP file (curl.php):
<?php
$ch = curl_init("http://getgrav.org/downloads/grav.json");
curl_exec($ch);
curl_close($ch);
Then run it from the command line:
$ php curl.php
You should get the output of the JSON:
{"version":"0.9.29","date":"2015-06-23T00:24:01Z","assets":{"grav-upda te":{"name":"grav-update-v0.9.29.zip","type":"application\/octet-strea m","size":2181661,"download":"https:\/\/github.com\/getgrav\/grav\/releases\/download\/0.9.29\/grav-update-v0.9.29.zip"},"grav":{"name":"grav-v0.9.29.zip","type":"application\/octet-stream","size":3400157,"download":"https:\/\/github.com\/getgrav\/grav\/releases\/download\/0.9.29\/grav-v0.9.29.zip"}},"url":"https:\/\/github.com\/getgrav\/grav\/releases\/tag\/0.9.29","changelog":{"0.9.29":{"date":"06\/22\/2015","content":"1. [](#new)
* New and improved Regex-powered redirect and route alias logic
* Added new `onBuildPagesInitialized` event for memory critical or time-consuming plugins
* Added a `setSummary()` method for pages
2. [](#improved)
* Improved `MergeConfig()` logic for more control
* Travis skeleton build trigger implemented
* Set composer.json versions to stable versions where possible
* Disabled `last_modified` and `etag` page headers by default (causing too much page caching)
3. [](#bugfix)
* Preload classes during `bin\/gpm selfupgrade` to avoid issues with updated classes
* Fix for directory relative _down_ links","content_html":"<ol>
<li><a href="#new"><\/a>
<ul>
<li>New and improved Regex-powered redirect and route alias logic<\/li>
<li>Added new <code>onBuildPagesInitialized<\/code> event for memory critical or time-consuming plugins<\/li>
<li>Added a <code>setSummary()<\/code> method for pages<\/li>
<\/ul><\/li>
<li><a href="#improved"><\/a>
<ul>
<li>Improved <code>MergeConfig()<\/code> logic for more control<\/li>
<li>Travis skeleton build trigger implemented<\/li>
<li>Set composer.json versions to stable versions where possible<\/li>
<li>Disabled <code>last_modified<\/code> and <code>etag<\/code> page headers by default (causing too much page caching)<\/li>
<\/ul><\/li>
<li><a href="#bugfix"><\/a>
<ul>
<li>Preload classes during <code>bin\/gpm selfupgrade<\/code> to avoid issues with updated classes<\/li>
<li>Fix for directory relative <em>down<\/em> links<\/li>
<\/ul><\/li>
<\/ol>"....