Hi. It's about not repackaging or reselling them as assets, they must be incorporated into a project. Meaning you can't simply re-upload or resell my textures elsewhere as your own, otherwise they're totally good to use in mods or games.
Regarding the logo, it was originally a Quake pack so it was supposed to evoke the logo while being its own thing (a horned skull and crossbones). I don't believe they own the rights to crescent horns or a detached spike, but that being said it's got me thinking it really limits their use, so I think I'll add versions that are simply traditional skull and crossbones soon.