If a project requires that contributors sign copyright over to a central party, that central party can later choose to release future versions under a proprieta

If a project requires that contributors sign copyright over to a central party, that central party can later choose to release future versions under a proprietary license and profit off of others' past work. A project that does not require central copyright assignment and that receives sufficient outside contributions cannot have that happen, provided it's licensed under something like the (L)GPL. Copyright paralysis can be a feature rather than a bug.