"The GPL, or any other software licence, depends upon the
framework of copyright law. Copyleft is a hack on copyright law
that puts the rights and responsibilities back into the hands of
"The logic of Richard Stallman and the FSF is that "a copyright
holder in a jointly-authored work is in a weak position to enforce
its copyright unless all co-authors participate in the legal
action". If all the authors participating in an open source project
assign their copyrights to the FSF this puts the FSF in a strong
legal position to act as an umbrella in defence of the GPL and any
code licensed under it.
"Ownership by a trusted foundation or non-profit gives some
assurance of the integrity of the licence, and the FSF copyright
assignment agreement promises to keep the code free; couched in
these terms, copyright assignment is probably a good thing."