Opal prebuilt binaries, err… compiled JavaScript files are available on:
Visit the link to have more detailed instructions
<head>
<meta charset="utf-8">
<script src="//cdn.opalrb.org/opal/current/opal.min.js"></script>
<script src="//cdn.opalrb.org/opal/current/opal-parser.min.js"></script>
</head>