I'm an author and want to make a couple cross-stitch patterns for inclusion in a mystery. Am I allowed to do that, or must I get permission to use the software for this purpose?
Please feel free to use KG-Chart for that purpose.
As long as those are your original design (in terms of copyright), there is no restriction using KG-Chart to design and distribute your own patterns.
I'd love to read your mystery with the cross stitch pattern involvement(?), so please let me know when you publish it! :)