Complex sentence: HAL for GNU/Linux OS was originally envisioned by Havoc Pennington and is now a freedesktop.org project, and was a key part of the software stack of the GNOME and KDE desktop environments.
Split into simpler sentences: HAL for GNU/Linux OS was originally envisioned by Havoc Pennington. It became a freedesktop.org project, and was a key part of the software stack of the GNOME and KDE desktop environments.