> concern that fragments of GPL code would end up in projects with non-GPL licenses
Framing it like this makes it sound like a problem with the GPL in particular, when really it's a problem for anything (including ingested code with no discernable license) that isn't expressly available under permissive licenses--more permissive than even the BSDs or MIT license, which after all, still require attribution by way of reproducing any copyright notices and distributing the text of the license itself.
The only terms where this isn't really a problem is limited to basically WTFPL and public domain code.
Framing it like this makes it sound like a problem with the GPL in particular, when really it's a problem for anything (including ingested code with no discernable license) that isn't expressly available under permissive licenses--more permissive than even the BSDs or MIT license, which after all, still require attribution by way of reproducing any copyright notices and distributing the text of the license itself.
The only terms where this isn't really a problem is limited to basically WTFPL and public domain code.