Adapts FAQ section in docs with Isaac Sim open-sourcing (#3105)

# Description

Some of the information in FAQ is now outdated since Isaac Sim is
open-sourced. This MR removes that part but also adds more explaination
on the goals of Isaac Lab.

## Type of change

- This change requires a documentation update

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

---------
Signed-off-by: Mayank Mittal <12863862+Mayankm96@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: ooctipus <zhengyuz@nvidia.com>

docs/index.rst

@@ -33,7 +33,7 @@ Isaac lab is developed with specific robot assets that are now **Batteries-inclu
 - **Humanoids**: Unitree H1, Unitree G1
 - **Quadcopter**: Crazyflie
 
-The platform is also designed so that you can add your own robots! please refer to the
+The platform is also designed so that you can add your own robots! Please refer to the
 :ref:`how-to` section for details.
 
 For more information about the framework, please refer to the `paper <https://arxiv.org/abs/2301.04195>`_
@@ -48,12 +48,13 @@ For more information about the framework, please refer to the `paper <https://ar
 License
 =======
 
-The Isaac Lab framework is open-sourced under the BSD-3-Clause license.
-Please refer to :ref:`license` for more details.
+The Isaac Lab framework is open-sourced under the BSD-3-Clause license,
+with certain parts under Apache-2.0 license. Please refer to :ref:`license` for more details.
 
 Acknowledgement
 ===============
-Isaac Lab development initiated from the `Orbit <https://isaac-orbit.github.io/>`_ framework. We would appreciate if you would cite it in academic publications as well:
+Isaac Lab development initiated from the `Orbit <https://isaac-orbit.github.io/>`_ framework.
+We would appreciate if you would cite it in academic publications as well:
 
 .. code:: bibtex
 

docs/source/setup/ecosystem.rst

@@ -83,15 +83,46 @@ be the single robot learning framework for Isaac Sim. Previously released framew
 and we encourage users to follow our migration guides to transition over to Isaac Lab.
 
 
+Is Isaac Lab a simulator?
+-------------------------
+
+Often, when people think of simulators, they think of various commonly available engines, such as
+`MuJoCo`_, `Bullet`_, and `Flex`_. These engines are powerful and have been used in a number of
+research projects. However, they are not designed to be a general purpose simulator for robotics.
+Rather they are primarily physics engines that are used to simulate the dynamics of rigid and
+deformable bodies. They are shipped with some basic rendering capabilities to visualize the
+simulation and provide parsing capabilities of different scene description formats.
+
+Various recent works combine these physics engines with different rendering engines to provide
+a more complete simulation environment. They include APIs that allow reading and writing to the
+physics and rendering engines. In some cases, they support ROS and hardware-in-the-loop simulation
+for more robotic-specific applications. An example of these include `AirSim`_, `DoorGym`_, `ManiSkill`_,
+`ThreeDWorld`_ and lastly, `Isaac Sim`_.
+
+At its core, Isaac Lab is **not** a robotics simulator, but a framework for building robot learning
+applications on top of Isaac Sim. An equivalent example of such a framework is `RoboSuite`_, which
+is built on top of `MuJoCo`_ and is specific to fixed-base robots. Other examples include
+`MuJoCo Playground`_ and `Isaac Gym`_ which use `MJX`_ and `PhysX`_ respectively. They
+include a number of pre-built tasks with separated out stand-alone implementations for individual
+tasks. While this is a good starting point (and often convenient), a lot of code
+repetition occurs across different task implementations, which can reduce code-reuse for larger
+projects and teams.
+
+The main goal of Isaac Lab is to provide a unified framework for robot learning that includes
+a variety of tooling and features that are required for robot learning, while being easy to
+use and extend. It includes design patterns that simplify many of the common requirements for
+robotics research. These include simulating sensors at different frequencies, connecting to different
+teleoperation interfaces for data collection, switching action spaces for policy learning,
+using Hydra for configuration management, supporting different learning libraries and more.
+Isaac Lab supports designing tasks using *manager-based (modularized)* and *direct (single-script
+similar to Isaac Gym)* patterns, leaving it up to the user to choose the best approach for their
+use-case. For each of these patterns, Isaac Lab includes a number of pre-built tasks that can be
+used for benchmarking and research.
+
+
 Why should I use Isaac Lab?
 ---------------------------
 
-Since Isaac Sim remains closed-sourced, it is difficult for users to contribute to the simulator and build a
-common framework for research. On its current path, we see the community using the simulator will simply
-develop their own frameworks that will result in scattered efforts with a lot of duplication of work.
-This has happened in the past with other simulators, and we believe that it is not the best way to move
-forward as a community.
-
 Isaac Lab provides an open-sourced platform for the community to drive progress with consolidated efforts
 toward designing benchmarks and robot learning systems as a joint initiative. This allows us to reuse
 existing components and algorithms, and to build on top of each other's work. Doing so not only saves
@@ -113,3 +144,12 @@ to Isaac Lab, please reach out to us.
 .. _OmniIsaacGymEnvs: https://github.com/isaac-sim/OmniIsaacGymEnvs
 .. _Orbit: https://isaac-orbit.github.io/
 .. _Isaac Automator: https://github.com/isaac-sim/IsaacAutomator
+.. _AirSim: https://microsoft.github.io/AirSim/
+.. _DoorGym: https://github.com/PSVL/DoorGym/
+.. _ManiSkill: https://github.com/haosulab/ManiSkill
+.. _ThreeDWorld: https://www.threedworld.org/
+.. _RoboSuite: https://robosuite.ai/
+.. _MuJoCo Playground: https://playground.mujoco.org/
+.. _MJX: https://mujoco.readthedocs.io/en/stable/mjx.html
+.. _Bullet: https://github.com/bulletphysics/bullet3
+.. _Flex: https://developer.nvidia.com/flex