In general, one can say that risk of license complications increases as an organization modifies a product (rather than using it as-is) and also if the organization distributes the product. There are no "good" or "bad" licenses; rather there are licenses more or less appropriate depending upon what use you plan to make of the licensed product. Mixing licenses can impose challenges, but these challenges are by no means insurmountable.
To understand what risks your organization may be faced with, you have to analyze your circumstances; so it is impossible to make any blanket statement without knowing those circumstances.
This was first published in February 2005