If I recall correctly, that was because it was legally uncertain whether a copyright infringement case could be brought by an entity other than the copyright ho

If I recall correctly, that was because it was legally uncertain whether a copyright infringement case could be brought by an entity other than the copyright holder in the case of GPL violations. Since then, lawsuits to ensure GPL compliance haven't really materialized, since the threat of lawsuits tends to be sufficient, so assignment of copyright hasn't been necessary for other similar foundations. Intent also matters, and I would trust the FSF much more than I would trust a Microsoft-based foundation.