The Lightstreamer 4.x versions work fine with JVM 1.7, indeed it's recommended for performance reasons as for Lightstreamer 5.x.

However, please note that Lightstreamer 5.x includes full support for WebSockets, a brand new JavaScript client API, impressive performance boost, and many new features. So in order to get all this benefits we highly recommend upgrading to the latest version, 5.x Colosseo, of Lightstreamer too.