My interest in open works began with the release of the Dungeons & Dragons SRD under the Open Game License. From there, I developed an interest in other open role-playing games and then open stories, photos, computer games, etc.
I've noticed the word 'open' being used pretty liberally in this group, for example to describe projects that are available on many platforms. Other people sometimes use it to describe games that are free-of-price or ones where supplements are encouraged.
That's cool -- open does have a pretty broad definition. But I thought it might be useful to discuss some terms with very specific definitions. That way, we can discuss 'open source' games without having them be confused with other 'open' games without open source.
Free Software, Open Source, FLOSS and F/OSS: These are four terms for what I will call 'libre'. Each term has different connotations and different movements deliberately use different terms. But a libre game is a FLOSS game, and a free software licence is an open source licence.
Libre: For a work to be libre, everyone must have the right to distribute and copy it in its original form or to adapt it and then distribute and copy it. Everyone must have the right to do so for commercial gain, if they so desire. However, the copyright holder can place some restrictions on your use of the work -- for example, you must include a copy of the licence with the work, you must credit the original creator, etc.
The SRD is a good example of a libre product. You can sell it, share it, change it, keep it the same, print it out, etc., without violating any laws. However, you do need to include a copy of the Open Game License, declare all Open Content and Product Identity, make any derivative content Open, etc.
Semi-Libre: This is my term for works that have all the rights of a libre work, except that you cannot distribute or copy them for commercial gain. Semi-libre works are not open source, they are not free software, they are not F/OSS or FLOSS.
Eclipse Phase is a good example of a semi-libre product. It's under a Creative Commons Attribution-NonCommercial-ShareAlike licence.
Pseudo-Libre: This is my term for works that may look like they're libre, but on further inspection they're not even semi-libre. For example, a game that doesn't allow derivatives or a game that only allows derivatives (and doesn't allow the work to be shared in its original form). Or, a game which is freely available online but which is still protected by copyright law.
Copyleft: Copyleft licences are a subset of libre or semi-libre licences. They say, effectively, 'If you use this work, then you must keep it under the same licence. If you change it, your changes must also be under this licence'.
For example, if I use the SRD (maybe I create a new prestige class), then all content that uses the SRD must also be under the Open Game License, just like the SRD is.
I hope this is helpful for you and isn't just information you already know. Feel free to ask any questions or discuss any thoughts you have on defining open.
Creative Commons offers a lot of options, including the license under which Eclipse Phase was published electronically.
Yup, the CC licences break down like this:
Libre: CC Zero, CC Attribution, CC Attribution-ShareAlike (copyleft)
Semi-Libre: CC Attribution-NonCommercial, CC Attribution-NonCommercial-ShareAlike (copyleft)
Pseudo-Libre: CC Attribution-NoDerivatives, CC Attribution-NonCommercial-NoDerivatives