Would it be alright to use a slightly modified version of the Foobar2000 license for an application of my own? I too have a closed-source program that I want to offer up free for download, but most "freeware" licenses are "free software" licenses (the former allows closed-source programs, the latter does not). The bulk of my license agreement would consist of the Foobar license with an additional line added in to prevent people from selling my program.

The Foobar2000 license would be perfect for my needs, but before I went ahead and used it I wanted to make sure no one would object.

Sure, though you might want to have a look at the BSD license, which our license is derived from:
http://en.wikipedia.org/wiki/BSD_License

Don't take my word as being authoritative here, but I think if you released your software with a slightly-modified version of the foobar2000 license, no one would notice or care.

...so long as you don't bring too much attention to it...

Uh-oh, I see your problem.

Shhh!

Cheers, Slipstreem.

Thanks for the OK, Peter. By the way, I took a look at the BSD license you linked and it seems that you turned a "free software" license into a "freeware" license..sneaky

Have you had a problem with people offering this program up for sale under a different name? I added in a line to the general Foobar license to cover such cases since I read about Audacity's problems and didn't even want to approach that issue with my software any time in the future.

I don't think anybody would succeed at selling it as it's already clear that people can't redistribute modified versions; selling unmodified copies of something that you can get for free would be completely pointless. I might add an extra line about selling too though, just in case.