Exports are out of the scope from the GPL. If you paint something with Gimp yourself it’s yours. If you get some image from a hollywood movie it would not belong to you just because you import/export it via Gimp. The same is true if the image was already protected via the GPL and you import it. You can’t just take an icon-set of a GPL software and use it in your program. However if an image that comes with some GPL software is meant to be under the GPL as well is a bit blurry ( The trouble with artwork and free software licenses - Linux.com ) because it must be clear what’s source and what’s not. ManuelBastioni Lab made this clear: manuelbastioni.com - manuelbastioni Resources and Information. - Makehuman as well: http://www.makehuman.org/license_explanation.php …others don’t make this clear and it may or may not be ok. I think both of them provided theses tools for the purpose in the mind that you can use those .blend files and still use the export in your game. Sometimes things get worse if you ask to much… anyway I don’t see a reason to use any of those as the Makehuman export is fine with weighting, with skeleton, you can use the eyebrow, hair, cloth, … I’m in doubt that you would save some time if you remove the skeleton and replace it (and the weightpainting). If you create some mesh yourself those tools could be handy.
https://creativecommons.org/publicdomain/zero/1.0/deed.en
Of course. But it’s really not that complicated to add some IK bones yourself ( https://www.youtube.com/watch?v=cGvalWG8HBU ). They don’t have any weights (so no painting and other time consuming stuff) you just have to add some Bone constraints to it.