In Unix computing, Ion is a tiling and tabbing window manager for the X Window System. It is designed such that it is possible to manage windows using only a keyboard, without needing a mouse. It is the successor of PWM and is written by the same author, Tuomo Valkonen. Since the first release of Ion in the summer 2000, similar alternative window management ideas have begun to show in other new window managers: Larswm, ratpoison, StumpWM, wmii, xmonad and Awesome. First versions of Ion were released under the Artistic License, Ion2 and the development versions of Ion3 were released under the GNU Lesser General Public License (LGPL). However, the first release candidate of Ion3 included a license change to a custom license based on the LGPL.  Since version 2, Ion has been scriptable in the Lua programming language.
As of September 17, 2009, Valkonen states he is unlikely to continue developement of Ion by himself. However, changes are still accepted through a review. 
Tuomo Valkonen, the author of Ion, has been at the center of several controversies concerning the licensing and distribution of his software, in particular the proclivity of major Linux and BSD distributions of making outdated development versions of Ion3 (the current unstable development branch) available as part of "frozen" software repositories. Often, such versions will include patches, such as for Xinerama or Xft support, both of which Valkonen disapproves on professional and personal grounds and has had removed from the main source tree. Yet, such distribution would seem to imply that the patched version is the official Ion3 package maintained by Valkonen himself, which he sees as unacceptable. Valkonen has even recently become an outspoken critic of the entire free software and open source movement (the "FOSS herd", as he refers to it) due to his perceived mistreatment at the hands of several major distributions, including Arch Linux, Debian, pkgsrc (NetBSD, DragonflyBSD), and FreeBSD.
On April 28, 2007, Valkonen warned the Arch Linux maintainers of possible legal action because the (unofficial) Arch User Repository contained scripts to install Ion3 with patches he did not approve of. Later on he did the same with the pkgsrc maintainer of the NetBSD project and the ports maintainer of the FreeBSD project. As of December 12, 2007, the development branch of Ion, along with other software by Valkonen, was pulled from the FreeBSD ports tree, after the author filed a complaint about outdated development releases still being available. Any version of Ion may still be installed from source code on any Unix system with proper libraries and dependencies.
Valkonen has implied in several mailing lists that he has become completely disillusioned with, if not openly hostile toward, the free software community in general. He plans to switch to developing strictly closed-source software for the Windows platform in the future, presumably following the stable release of the Ion3 branch. Subsequently the author has indeed given up on Linux and become a Windows user.
- ↑ #422527 - ion3: New upstream release available - Debian Bug report logs
- ↑ On continuing Ion development
- ↑  - FreeBSD Ports Mailing List
- ↑ [tur-users] Ion3 trademark infringement
- ↑ tech-pkg: Outdated ion3 pkgsrc in violation of the license
- ↑ FreeBSD Mail Archives
- ↑ Ion3 license violation
- ↑ Ion3 removal (Re: Ion3 license violation)
- ↑ Ion3 license violation
- ↑ Not a blog: Defection? Part 3: Windows
|Techniques||Tiling · Stacking · Dynamic · Compositing · Re-parenting|
|Tiling Examples||dwm · PWM · Ion · Wmii · Ratpoison · xmonad · Xerox Star · Windows 1.0 · GEM (2.0 and Later) · Awesome (window manager)|
|Stacking Examples||twm · mwm · FVWM · Enlightenment · Blackbox · Presentation Manager · Windows 2.0 · Windows 95 · Windows 98 · Windows Me · Windows NT - Windows XP · Mac OS 9 and earlier · GEM 1.1 · WindowLab · Xerox Alto|
|Compositing Examples||Beryl · Compiz · xcompmgr · Desktop Window Manager (with Windows Aero) · Metacity · KWin · Aqua (with the Quartz Compositor)|