@FreedomCrusade: All works on OpenGameArt.org can be used commercially as long as you abide by the restrictions of the license. Here is a quick breakdown of the CC/OGA licenses (I am not a professional on the subject & suggest you read the summary in the links for each):

Note: You can also get to these summaries by clicking the icons for each license under the "License(s)" section of the submission.

• CC0
• Author has revoked all rights to the work. You can use, modify, & redistribute it for essentially any purpose, even without giving credit to the author.
• CC BY 3.0
• CC BY 4.0
• Works can be used, modifed, & redistributed for essentially any purpose. Author retains rights to work & must be credited/attributed. Author can require additional stipulations such as requiring user to link back to OGA.
• OGA BY 3.0
• Essentially the same as CC BY, but removes a restriction on using works within DRM projects.
• CC BY-SA 3.0
• CC BY-SA 4.0
• The most restrictive of the CC licenses allowed on OGA. Same stipulations as CC BY, but any usage, redistribution, or modification must be under the same or a compatible license. Similar to the restrictions of the GPL.

Edit: Anyone with corrections, please comment.