Version 4.0.1 is here!
This version(with 4.0.0) includes a ton of changes!

For simplicity i will just stuff the changelog here

  • Rewrote the client into an API/Framework
  • New Wx based download dialog
  • Official support for addons! (still needs a gui for users to add addons to the updater)
  • Removed dependency for grep, wget and curl (wget and curl are used as fallbacks only)
  • Improved the speed on deleting the maincache on windows
  • Changed internal file structure to be more organized
  • Legacy scripts for launching parts of the client (ex: rsu-settings)  are provided in this version until version 4.0.2 or 4.0.5
  • Download progress dialog for windows and mac
  • Client launcher now uses the runescape news rssfeed so dependency for libwebkitgtk1 is removed
  • Launcher works on Wx2.8 now
  • If wxperl is installed, the launcher will start if rsu-query is called without any parameters. If wxperl is not installed, it will start runescape.
  • Removed dependency for p7zip/7zip on mac and windows (using native tools instead)
  • Improved the look of the updater.
  • Fixed memory leak in the client launcher.
  • Let addons with info.conf at their root add themself to the updater!
  • Add support for using the download gui with wget and curl
  • Add support for running the launcher on older versions of perl (proper support for ubuntu10.04+)
  • Running for the first time will now automatically download the jagexappletviewer.jar instead of asking you to update.
  • Made launcher fetch news and do other time consuming operations in new threads.
  • Support for Old School RuneScape

You can get the new version from the PPA, AUR or Universal Archive