Unfortunately, I keep finding WordPress plugins that try to call cURL functions directly. Unfortunately, not only do these plugins fail to work if cURL isn’t installed, it throws a fatal PHP error in the process.
The problem with using cURL in WordPress plugins is that WordPress solved that problem more than 2 years ago by implementing the WP_Http class. WP_Http is a class included in the WordPress core that has multiple options. One of those options is cURL, but it gracefully reverts to other PHP functions if cURL isn’t available.
Basically, anything you can do with cURL can be done with the WP_Http class, and it will allow your plugin to be much more versatile and compatible with more server setups.