Use it however you want, really.
Also, on the comment "... not actually trying to sell blender to other people.". I believe you can do that too. However, why anyone would buy free software might be a bit of a "marketing problem"...
What you can't do, is take the source, modify it, keep the modified source to yourself, and then sell 'your modified version'. THAT isn't allowed. But just slapping the downloaded program on a CD and charging someone $10 for it...yup. You can do that. Of course, you have to also provide all the source code for your 'modified' version if someone askes for it.
It's all in the GPL stuff on the main Blender site.