I believe that by the sheer act of these demos being available through public domain collections, the authors have released (whether intentionally or not) their rights to ownership and thus stop anyone making copies of their works.
They may still hold copyright of the work - depending on the country the creaters were from, the year that the program was created and whether or not they have the copyright symbol somewhere in their production.
I agree that j_tramiel cannot sell the DVD as his own work, but he seems well within the law to charge a modest extra for his time, materials and effort for creating a compilation of public domain works.
