Few years ago, they sold these books without silly additional license. Rights of owners were implied by type of work. Then someone was a little afraid how it could be compatible with current copyright, and they added that license to allow explicitly at least minimal rights for users.

I would be very offended if someone would use GNU license for this type of work. Either put it into the public domain, or allow author rights as defined in EU (This means NONTRANSFERABLE author rights). Actually there is an additional problem. This isn't software. It contains algorithms (noncopyrightable), stories, descriptions, and images (all three copyrightable, and copyrighted in a reasonable way). So using software license for this would be idiocy (and would violate certain traditions).

So your choices are:
Do it for your home usage. Then you can copy it completely and if police will not find it you are without problem.
Use it in freeware. You could have mail them for permission and explain them that part about freeware. If they will not give you a permission, you might mail to SJ Games.


(Of course if you'd get to the court for a case that is against reason, and judge would not be able to understand any of implied rights of users given by tradition, you can tell the judge, the author of one of these games said he is an idiot.)