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Comment by dmc | Hacker News Reader

What about if a developer were to now download the source code available here? Could they, in theory, develop with it as they've never attempted to reverse engineer it themselves?

By using ToS, you're limiting enforcement to the people who do the RE, rather than an implementation, surely?

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Actually, no. If you look at those files, you're "tainted" and can't be the one who writes a new implementation. The correct way to do reverse engineering for compatibility is to have to completely separate teams. The first does the reverse engineering and writes the specification/documentation. The second completely separate teams takes the specs/docs and writes an entirely new implementation.

This is the process used to achieve the "IBM PC Compatible" system you're probably using right now (including your Mac). Reading up on the development of the Compatibles is a good way to understand how to do reverse engineering correctly.

Of course that was not the way the "IBM PC Compatible" market arose. IBM published a rather complete set of documentation of the system, including all interface signals and the BIOS source code. I still have several of those documents on my shelf. It is completely different from the complete lack of Skype technical documents.

IBM released documentation after the PC had been cloned through "clean room" reverse engineering.

http://en.wikipedia.org/wiki/IBM_PC_compatible

Then the cloners moved at warp speed. According to Wikipedia, the PC AT shipped in 1984. For nostalgia, I kept my copy of IBM Personal Computer Hardware Reference Library Technical Reference, Pub #1502494.

"This manual describes the various units of the IBM Personal Computer AT and how they interact. It also has information about the basic input/output system (BIOS) and about programming support.

The information in this publication is for reference, and is intended for hardware and program designers, programmers, engineers, and anyone else who needs to understand the design and operation of the IBM Personal Computer AT."

It includes the source listing of the PC AT BIOS, as well as complete interface pinouts, etc.

The colophon for this manual reads

First Edition (March 1984)

So what is your time line for IBM only publishing this manual after the PC AT was cloned?

The first IBM PC was publicly released for sale on August 12, 1981.

The first "100% Compatible" was the Compaq Portable in 1982. It wasn't the first "compatible" to market, but it claimed to be the first that hit the "100%" mark and validated the clone market.

I was an early Compaq employee. The documentation produced by the research team was vetted for anything not descriptive of behavior, then forwarded through lawyers, who logged each document, to the engineering team designing Compaq's compatible BIOS from the functional specs. A weird side effect: the process reproduced BIOS-level bugs for complete compatibility.

> The correct way to do reverse engineering

You should always emphasize that its the correct way _in the US_. As somebody already mentioned, HN readership is international, and said restrictions on reverse engineering do not apply everywhere. Also the author, judging by his name, doesn't seem to be a US citizen.

Technically the "tainted" attack could even come from programming books that offer code snippets. Unless you have a signed release from the copyright holder of the book, you are also tainted.

Abstrd, but true according to what you're saying, if you can prove that I copied it. Now, assuming you did download and peruse the source code for Free_skype: fine. Now prove it.

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