PySoy is available under the GNU Affero General Public License v3.

Our intention in using this license is to promote the development of copyleft games which ensures that players have the freedoms to play, contribute to, and share the games with others. Below is an explanation of what this means for game authors.

What is Copyleft?

The PySoy engine is a copyrighted software product. Like most copyrighted works, it may not be used, modified, or redistributed without a license.

This is where the AGPLv3 comes in; this is the license which permits PySoy to be used, modified, and redistributed. It also allows you to create, distribute, and even sell PySoy-based games. By downloading a copy of PySoy or a PySoy-based game you receive these explicit rights.

There are no royalties, licensing fees, or other monetary requirements for using PySoy. When you create games based on PySoy, however, that entire game must also be available under the AGPLv3. This means everyone who receives a copy of your game or plays it over a network may change it, redistribute it, and they too must release their changes under the AGPLv3.

This is what the term "copyleft" means; we're inverting the copyright paradigm.

What about art and music?

The AGPLv3 clearly defines the scope of the license in section 5c:

    c) You must license the entire work, as a whole, under this
    License to anyone who comes into possession of a copy.  This
    License will therefore apply, along with any applicable section 7
    additional terms, to the whole of the work, and all its parts,
    regardless of how they are packaged.  This License gives no
    permission to license the work in any other way, but it does not
    invalidate such permission if you have separately received it.

In case "whole of the work, and all it's parts" is not clear enough, every part of a PySoy-based game must be under the AGPLv3. Digital art and music is as much part of the software as instruction code. It does not matter if it's distributed in a single file or multiple files, "regardless of how they are packaged", all parts of the game must be licensed under the AGPLv3.

When your PySoy-based software includes the ability to present external media to the user, such as the case of a video or music player, where the media has no special configuration or orientation specific to the PySoy, copyright law (and thus the AGPLv3) does not extend to that arbitrarily loaded media.

Third party media, such as "clip art" textures and "free" sound effects, may only be used in PySoy-based games if the license on that work is compatible with the AGPLv3. In cases where the content is neither public domain or an AGPL compatible license the author of that work may be contacted to request it also be available under the AGPLv3. We are working to build our own library of textures, models, music, and sound effects for use in PySoy-based games.

What about the GNU GPL?

The most popular copyleft software license is the GNU General Public License, which the AGPLv3 is based on.

Software licensed under "GPLv2 or later" can be upgraded to GPLv3, and GPLv3 licensed software can be upgraded to the AGPLv3 under section 13 of that license:

  13. Use with the GNU Affero General Public License.

  Notwithstanding any other provision of this License, you have
permission to link or combine any covered work with a work licensed
under version 3 of the GNU Affero General Public License into a single
combined work, and to convey the resulting work.  The terms of this
License will continue to apply to the part which is the covered work,
but the special requirements of the GNU Affero General Public License,
section 13, concerning interaction through a network will apply to the
combination as such.

Thus while a PySoy based game must be AGPLv3, as by nature it's a combined work, it may utilize other software (libraries, media, etc) licensed under any GPLv3 compatible license.

How do I license my game?

Just as the PySoy source code embeds the AGPLv3 template at the top and in the credits property, you may (and should) do the same. All your game's media files, in case they are somehow obtained separately, should also be tagged for the AGPLv3 (.soy exporters do this automatically). You should also include a copy of the AGPLv3 LICENSE file with your game.

Each PySoy-based game should also include, through the game's splash, title, or menu, a clear statement that it is based on PySoy and licensed under the AGPLv3. PySoy includes the splash functions for doing this. Requirements for this are detailed in section 5d:

    d) If the work has interactive user interfaces, each must display
    Appropriate Legal Notices; however, if the Program has interactive
    interfaces that do not display Appropriate Legal Notices, your
    work need not make them do so.

How can I make money?

We all know the proprietary software model; produce software then charge money for others to use it. Some people buy it, others receive illegal copies from those who purchased it, and the producer hopes there is enough of the prior to make it worth his time. A good deal of "anti-piracy" measures involve adding value to purchased copies; attractive packaging, added support, priority access to updates, etc.

This can work for copyleft software as well, except we don't call it piracy since copying is legally permitted. The same value-added tricks to encourage purchase applies. However, the concept of games as a "product", something static that you buy, consume, then discard, is disfavorable to us. We can do much better with "gaming as a service".

This model is: build the basic framework, then players pay for the service of custom, interactive playing experiences. An RTS game may include "research" for tech thought up by the player, which is then unique to them. Teams of players may find themselves facing unique challenges, the game's story may weave dozens of players together, players may even have the ability to "sketch" new clothing or ships to be designed. There may be a subscription for this or the service to create such custom items may be paid for ala-carte.

Remember: software freedom is the best "selling point" you could ever have. The proprietary game market is flooded, copyleft game are low supply and in an ever-growing demand, it doesn't take a business guru to see where the money's to be made.