The Plate & Case Builder is offered free of charge to anyone who finds it useful. By using this builder you are by no means expected to donate. That being said, I dedicate quite a bit of time developing and updating this tool, so if you feel like buying me a beer (or two), it is always appreciated.
I value your feedback, good or bad, so please feel free to get in touch. If you have questions or problems, please post in this GeekHack thread. By posting there others can benefit from the conversation and can weigh in with their feedback as well. If you want to contact me directly, you can message me on GeekHack.
I wish you the best on your keyboard building adventure.