Vegan with substitutions

I bought a new cookbook today. I'm a total cookbook addict so it's not a huge surprise. I spent the gift certificate that D. had given me for my birthday last week on "Vegan with a Vengeance" by Isa Chandra Moskowitz. She's one of the authors of the vegan cupcake book I have that I used for my cupcake party. I debated for a long time between this one and her most recent one called "Veganomicon". It's essentially a Joy of Cooking for vegans. Looks great and has some nice coding of recipes so you can find ones that cook quickly or don't have soy or something. But I found that this one (Vegan with a Vengeance) has a more personal voice to it. I don't always like that but in this instance I think I like her personality so it works for me.

Once bought of course I felt the need to make something out of it. So tonight's dinner will be "Coconut Rice with Toasted Coconut", "Jerked Seitan", roasted root veggies, baked butternut squash, and sauted greens. Well, it won't be exactly that. Those are the names of the recipes I'm using but alas I've had to make some substitutions. I think substitutions are the nature of cooking and a sure sign that you've transformed your cooking into a higher art. I didn't actually have the jasmine rice the "Coconut rice" recipe called for so I'm using short-grain brown rice. There is a brown jasmine rice (and I thought I still had some left in the pantry) but this was not worth going back to the store. It also calls for finely grated lime zest. No limes, sorry. I don't even think I will put the toasted coconut on it at this point. Too much effort.

I also couldn't find seitan at my local market (even though they had some a mere few weeks ago! Damn you Real Foods!) So tofu it is, as a fine substitute. I didn't have enough dried thyme for the marinade either so I added oregano. And I'm going to omit the green pepper. So my real question is this: at what point does someone else's recipe become your own? Copyright people, can you let me know? I have to deal with a lot of permissions issues at my job. I'm curious about how it works for cookbooks. One ingredient different- is that enough? Different amounts? What about classic recipes, a la Joy of Cooking?