The products mentioned in this thread have pretty different properties. I get my info on this from
Bob Flexner's book which I recommend highly. Huge amount of scientific info on finishing products. The chemists I know say it is accurate.
Lemon oil is scented petroleum-distillate solvent. It does a good job of cleaning gunk off a fingerboard and leaves the board shiny and smelling like lemons for a short time. It does not provide any type of barrier to moisture.
Boiled linseed oil is made from flax oil that has been heated. It will penetrate the wood and darken it, and oil left on the surface will cure to film finish, but the film is very soft so it must be left thin. It provides some barrier to moisture.
Tru oil is linseed oil that has been "polymerized" by heating (further than boiled oil) to 500 degrees in an oxygen free environment. It cures harder and provides a better moisture barrier than other types of oil finishes. It can be wiped on like other oil finishes.
I don't know what "butcher's block oil" is, but I would guess that it is based on something tasetless and nontoxic like mineral oil, (which is what I use for cutting boards).
I use lemon oil to clean unfinished rosewood or ebony boards when needed, but my hands are rather dry and not as acidic as some people's.
The products mentioned should all be safe if you use good safety precautions for flamable liquid. Any good book on woodworking should give good tips.