I agree with Danke. Legally you don't owe taxes unless you work for the government or take government handouts, but ultimately if Barney Fife wants his money he will come and take it, using violence if necessary, whether or not they are following the letter of the law. Technically the way the income tax laws are written, "Income" means, money derived from tax payer sources. So if your money doesn't come from tax payers like teachers, police officers, politicians do, then you don't make "Income". But like I said, the people who come to collect don't care about laws because the law is what ever they say it is while they have a gun in your face on your porch.
If your still interested read "Cracking the Code" by Pete Hendrickson. This is the information that Danke talks about and is my beliefs as to the truth extent of the law. People who would tell you otherwise, ignore the supreme courts own ruling (twice) that the 16th Amendment added no new powers of taxation. The Supreme Court is right and our tax code is being applied to the wrong people under the threat of force. When you send in a 1040 your actually perjuring yourself but I'm pretty sure they will never come after you for that offense.