<<I think the license answers this one: there is no requirement to
reproduce the PI declaration, as there is the copyright notice. If
PI was supposed to inherit, then you'd be required to add to, rather
than replace, the PI declaration, i'd think.
>>
If the contributors collectively grant you a license, then effectively you'd have a license with each of them, and be responsible to meeting each of there terms.
I don't think the license makes this clear at all. There is some type of allowance for the creation of a "child license" that's a duplicate of the "parent license" and it's unclear whether you are agreeing to that license solely with the last guy in the chain, or along with all the other Contributors, since the license says the "Contributors grant you a license", multiple contributors granting a single license.
Lee
