The bottle of Tru-Oil warns that it will burn if you ignite it, and poison you if you swallow it. It doesn't mention the need for ventilation or masks. I use it indoors without any problems. I would't advise you to keep a freshly coated neck or body in your bedroom because you may not like the smell, but it won't harm you.
One warning that is traditionally given for all oil finish products: linseed oil, tung oil but also Tru-Oil, is to be careful with disposing of rags or tissues that you have used to apply it. In the drying process (a polymersation) heat is generated and this could lead to spontaneous combustion. I'm not sure how often this has actually occurred with the quantities you would normally use when finishing a guitar, but it's better to err on the safe side than to wake up dead due to your house burning down...