Can a 401(k) plan accept a rollover from a keogh? The CEBS textbook says yes, and give no qualifications. However, if a Keough can be set up as either a DB or a DC plan, wouldn't there be restrictions?

Generally, a qualified plan (which allows for rollover contributions under the document's terms) may accept a rollover from another qualified plan. Since the money coming out of the first plan is coming out as a distribution, it is not relevent whether the distributing plan is a DB or a DC. Keoghs are simply qualified retirement plans for self-employed individuals. However, as the receiving plan, I think I would ask for verification that this plan is qualified. Unfortunately, there are quite a few Keoghs out ther that have not been kept up to date.