I wouldn't make more than one plane, because I think it is stealing.
Okay, so you're violating the letter, but not the spirit, of the law, correct? You do not hold an original RAF license. Yet you built an airplane from those plans anyway. Technically, it's not a legal set of plans even if they had not been used to build an airplane before you bought them, because you are not the license holder, right? (The license on my TERF CD specifically authorizes "the undersigned"...the person who signed the license...to build one airplane.) From a strict LEGAL standpoint (speaking as a layman, here), your set of plans is no different from an unauthorized copy, because of the lack of license. Ethics are another matter.
Are you stealing? I don't think so, and evidently neither do you. That's pretty gray in my book.
What you did not say is whether an airplane had already been built from those plans, by the guy who sold them to you. If so, then please explain to me exactly how your set of original, used plans is in any way different from a copy (one set, one airplane). If not, exactly how do you KNOW they have not been used to build a plane?
What if I purchased an original set of plans that was missing one or two templates through loss or damage, and that had not been used to build an airplane? Would it then be okay if I obtained a copy of said missing/damaged templates to build a single airplane from those plans?
Is THAT stealing?
It IS copying.
A question you did not answer: Is it theft if I WANT to pay the copyright holder for the right to use the material, but the copyright holder won't accept my money? Legally, I suppose the case could be made...but ethically? You've already demonstrated that not actually holding a license has not stopped you from using the plans to build an airplane. Therefore it's not the license itself that's at issue here, from an ethical standpoint. It's whether the plans are original or not.
If you look at your reply about the software, it seems to be exactly the same situation. In the case of nontransferrable licenses, you say you'd take the software off the machine...yet it's okay to buy that set of plans and use them, even though RAF has explicitly said that the license is non-transferrable? It's clear that you believe you're on solid ethical ground, and frankly I agree with you.
But it seems equally clear to me that you are NOT on solid legal ground, and that in fact your set of plans is illegal and should never have been used. The fact that there are many, many EZ builders out there who have done exactly the same thing doesn't change that.
If this is truly a black and white issue, then anyone who does not hold a bona fide orginal license from RAF is in violation of copyright law and is not authorized to build an airplane. That's what "non transferrable" means, right?
It's frustrating to WANT to do the right thing, but be stymied by circumstance and policy. If I have the opportunity to do what you did, chances are I'll take it and use the same logic you have...which in my opinion is a good, common-sense view, despite what the lawyers might say.