Using OpenTTD resources for a different game

[Ruiluth]

Hi all, sorry if this question has been discussed before, but I wasn't sure how to find out for sure.

Basically, I want to create a new game which will use isometric graphics, and I was wondering what the legality of using OpenTTD graphics as a base would be. Since OpenGFX is licensed under the GPL, I'm assuming that I'm free to use and/or modify it to suit my purposes. I'm also assuming that most NewGRFs would be difficult or impossible to acquire files and/or permission for. Does that sound like a correct analysis? Is there anything else I need to know?

Thank you all for your help.

[Gwyd]

I'm not sure about the first part of your question, but regarding NewGRFs, most are released under one of the GPLs. This means that getting hold of the source code and graphics isn't usually too hard. Many of them frequently have online repos (look at OpenTTD Coop) or a .zip may be in the op of a forum post. This doesn't apply to all GRFs, so always check the license.

[kamnet]

If the source files are covered under GNU Public License, you're free to use them as you wish so long as you abide by the license. As noted by Gwyd, many NewGRF projects are licensed under GPL as well. Many projects also use other license, such a Creative Commons, some are even released into public domain, but many also do not have a license or contain a non-free license. For those you may need to get explicit permission from those who created the files in order to use them.