Tru Oil is polmerised linseed oil, at least that is its main constutient.
"Its unique blend of linseed and natural oils"
Danish Oil can often contain either tung or linseed oil, or both, and other things. And posibly the oils have been modified aswell.
So, it is best to stick to a brand of oil that people recomend because a tin of "Tung Oil" or "Whatever Oil" could be mostly pure, cut with other oils, polymerised, added solvents, or added anything. It could even contain no "Tung Oil" at all!
There is a wealth of info on this subject in the library of archived messages at MIMF.
http://www.mimf.com/
You will need to register, and its not an easy site to navigate, but there's loads of great info there, around 30 archived threads just on oil finishes.
chris