How do I delete iTunes library without removing them from iPod?

after a certain amount of time your iPod will require a resync to update license, if you delete the songs you may need to repurchase them. I am not entirely sure but if you change the settings on your ipod so that you update it manually rather than syncing it you might be able to delete them. well first sync it once then change your iTunes setting so that it doesn't automatically sync songs when you connect your ipod then delete your songs of your computer