Some issues raised by your post that I feel should be addressed to clarify the definition of stealing:
There may be a difference between the legal definition of stealing and the "moral" definition, for lack of a better term. What may be legally permissible may be morally wrong.
In the example you gave re: Einstein's findings, I would readily agree that the example is not theft. But if another scientist published Einstein's conclusions under his own name, even without any plagiarizing of text, that would be wrong.
Going into the field of music and the theft vs. influence question, I also assert that Goodman was in no way was a theif for using Henderson's sound as a basis for his. As you and others pointed out, he paid for the arrangements, modified them to his own style, and actually hired Henderson as an arranger.
In the example of Lester Young and Stan Getz, we are in a more gray area. I don't know if Prez ever tutored or instructed Getz, but if he did, then it was a teacher/pupil situation and Lester clearly willingly participated. But, if as I seem to recall, Getz merely copied Lester's style on his own, then Prez had some justification to feel he was robbed. As a counterargument to this, we must deal with these two points: 1)there is no legal copyright on a musical style ( plus, how closely would the 'theif's' style have to be ); and 2) we must consider the fact that, given the racial climate of the time, Lester Young could never make the money and success that Getz could, anyway!
If only Prez had lived until the sixties- maybe we could dig his version of Girl from Ipanema!