I think posting the output of the design file is not illegal, however, it would mean that the others need to have the same software to use the file. One only need the deisgn file if they want to change it themselves.
If you are going to provide the design files of the PCB. make it a GERBER file. All PCB maker should accept this file type.
For the circuit diagram, make it PDF file.
AFAIK, it should be fine to reuse anything that is provided on Cypress website. As long as you dont mess with Cypress's copyright material, it should be fine.
For schematic and layout, all you need is the software and experience with PCB designing. You need to be careful because, PSoC3 board design will be a mixed signal design. Make sure you take good care of the analog components. You can use CY8CKI-030 as the reference. It is a pretty neat design with separate ground planes for Analog and digital part. It also has a very complex and robust power supply unit. There is very good app note on hardware considerations for PSoC3. There is one more App Note on Pin selection. A careful design with some considerations on Pin requirements for different purpose should result in a robust design.
Hello, I also enquired with kits team here. You are free to reuse the layout and schematic files that Cypress is provided. Only restriction that Cypress lays down is from selling the exact same replica of the board. As long as you make some changes to the board use, you should be alright.