Therefore, it automatically downloads when trying to login. They provide the clients in their appliance build releases and only the necessary version is included with the build. Having the software is legal but you can't use it with anything else. In fact, network connect was licensed separately on top of this, but I digress. Their licensing is all back-end and based on concurrent sessions. It is not available 3rd party or from non-admin download from Juniper.

That way there is no confusing the correct version needed. More to the point of answering your question, Juniper wants you to get it directly from whatever system(s) you're connecting to. This link lists the supported OS/apps in V7.1r4.0. If its 6.x or 7.x, things will probably be ok. Like I mentioned earlier, later builds seemed to expand support for Ubunto and Linux in general. I can't remember which specific build was stable for Network Connect in Ubuntu, but I do remember seeing Juniper documentation specifically naming certain versions of Ubuntu in their 'supported' OS section.

Over time, Juniper released more features and support of Ubuntu in general. Newer builds typically have expanded support although this hasn't always been the case. The answer depends on what build & release of the SA software is installed on the Juniper devices.

Juniper network connect software