I think it is very fair and reasonable, Nick. When I design a tartan, part of the fee is for the design work and part of the fee for the production of the cloth. So if someone wants the cloth produced elsewhere, that's fine because I still charge for the deisgn work.

Here, you are not actually providing the design work, but providing the means for the client to do his own design work. As you have said, the development of that means has been quite an investment for you.

There are really only two ways to handle it, in my opinion -- 1) charge people to use the design software, or 2) make the use of the software free, but ensure that you get the cloth purchase from the design.

I think number 2, which you have chosen, is a very user-friendly option that allows the potential customer to expirament a little without any cost or risk. But it is important that people to do take advantage of the software be aware of the Terms and Conditions they are agreeing to.

Back to Rex's tartan -- I've said it before but it bears repeating -- splendid design!