Filter Forge is a Photoshop plugin that you can use to create your own texture filters. It is also a standalone filter creator.
http://www.filterforge.com/
The Intellectual Property Statement on the site itself says:
http://www.filterforge.com/termsofuse.html
Intellectual Property
Copyright, trademark and all other proprietary rights in the Content (including but not limited to software, services, audio, video, text and photographs) rest with Filter Forge and/or its licensors. Unless otherwise specifically provided herein or authorized by Filter Forge in writing, all rights in the Content not expressly granted herein are reserved. You agree not to copy, republish, frame, make available for download, transmit, modify, rent, lease, loan, sell, assign, distribute, license, sublicense, reverse engineer, or create derivative works based on the Website, its Products or its Services. Except as otherwise provided, the Content published on this Website may be reproduced or distributed in unmodified form for personal non-commercial use only. Any other use of the Content, including without limitation distribution, reproduction, modification, display or transmission without the prior written consent of Filter Forge is strictly prohibited. All copyright and other proprietary notices shall be retained on all reproductions.
Filter Forge hereby disclaims any rights to trademarks, service marks, trade names, logos, copyright, patents, domain names or other intellectual property interests of third parties. All intellectual property interests of third parties referenced herein or otherwise provided on this Website are the properties of their respective owners. Filter Forge disclaims any proprietary interests in the intellectual property rights other than their own.
The FAQ on the Filter Forge Wiki states:
http://www.filterforge.com/wiki/index.php/10q
You can use the Filter Library filters for commercial or non-commercial purposes as long as you don't violate the law or someone else's rights.
It is ok to modify other filters to your convenience. If someone's snippet or filter inspired you to create your own filter, it is considered polite to mention the author of the original idea in your filter info.
And finally, someone who uses Filter Forge to create and sell textures in SL offered this:
If you are talking about textures produced by filters which you create yourself -- no, there are no limitations and there won't be. You are the copyright holder for the filters you create. If you are talking about textures produced by filters created by other authors -- under the current Filter Forge EULA, there are no restrictions for using the textures for commercial or non-commercial purposes, including selling the textures. However, the next version of Filter Forge EULA will most probably introduce such restrictions. For more information on copyrights and the new EULA, please see http://www.filterforge.com/forum/read.php?FID=5&TID=4542 Best regards, Bella Beygelman, Filter Forge Support, [email]support@filterforge.com[/email]
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According to the Filter Forge forum post, it is legal to sell textures you find on the Filter Forge site, even though to me the current EULA states that it isn't.
Am I missing something here? If this is true it's definitely a buyer beware issue, since these textures can be purchased in world yet are free on the web.