Is it called research misconduct when someone publish his own work under the name of other people?
This does not sound ethical at all. I would say that both your friend and the people who are willing to take credit for his work are lying and misrepresenting their accomplishments.

Furthermore, what your friend is doing is extremely short-sighted. If the material in his publications is remarkable as you state, then he will gain far more citations in the long term by having his name on all of them, rather than trying to artificially inflate his citation count for short-term gains.