Question about scratch copyright

Here's some additional info from the lead programmer of Scratch...

Hi, Amos.

Here is my interpretation:

The author of any modifications to Scratch owns the copyright to any
new code that they write. The copyright for their code is NOT
automatically assigned to MIT. MIT could not, for example, include
their changes in a Scratch release without their permission. However,
under the "share alike" clause in the Scratch license, they must share
the source code for their changes. "Share alike" clauses are quite
common in open source licenses.

A derivative work is bound by all the terms of the Scratch license,
including the non-commercial clause, so creators of modified or
extended versions of Scratch cannot sell their derivative works
without permission. However, anyone who modifies Scratch is allowed to
use and their distribute derivative work for free or use it in other
ways.

For example, the Open University created a modified version of Scratch
that they hope will be used by over 10,000 students over the next five
or six years. They are allowed to do that under the terms of the
Scratch license.

Note that the Scratch source license is irrelevant to people who
merely wish to use Scratch (which includes most students and
educators). The license for the "binary" Scratch packages does not
even include a non-commercial clause, so people can, for example,
distribute it in an educational package or package it with a book.

I hope that helps clarify matters.

	-- John