The Debian project and Nathanael Nerode have raised objection. Debian developers eventually voted to consider works licensed under the GFDL to comply with their Debian Free Software Guidelines provided the invariant section clauses are not used. These critics recommend the use of alternate licenses such as the share-alike Creative Commons licenses, the BSD Documentation License, or even the GNU GPL. They consider the GFDL a non-free license. The reasons for this are that the GFDL allows ""invariant"" text which cannot be modified or removed, and that its prohibition against digital rights management (DRM) systems applies to valid usages, like for ""private copies made and not distributed"".