Have you ever witnessed this?
Why on earth would OS X keep 3.97 GB of inactive memory rather than releasing it? I think it's to let closed programs launch faster but frankly, I closed the program on purpose so I wish I could turn this off. While I haven't found a way to turn off this feature, there is a way to circumvent it - pronounced cirsumvent by anyone in the know - and get your RAM back.
If you have xcode installed you already have a command-line tool. Just type "purge" in the command line and voila:
If anyone knows of any problems with this, please reply in comments and let us all know!