The relation in expression (6) does not require any assumptions about the discount rate that are not already embedded in the dividend discount formula in expression (5), that is, even though Ohlson (1995) and Feltham and Ohlson (1995) are developed in a world of risk-free discount rates, one can substitute the cost of risky equity capital, so long as one is willing to accept the assumptions underlying the use of the same risky discount rate in expression (5). Alternatively, one can avoid those assumptions altogether, by computing a risk-adjusted earnings number and discounting that at the risk-free rate (Feltham and Ohlson 1994).
The relation in expression (6) does not assume any of the linear infor
mation dynamics in either Ohlson (1995) or Feltham and Ohlson (1995).