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Comment by jordigh | Hacker News Reader

While we're talking about stats and Python could I convince someone here to implement a fast medcouple for statsmodels? I can't do it myself because I read R's GPL'ed code in order to understand the algorithm. Using my understanding, I wrote the following high-level description of it:

https://en.wikipedia.org/wiki/Medcouple

This should be taken as the design spec of a clean-room reverse engineering, so that we can have a free, fast and non-copylefted implementation. It's not that I have a problem with copyleft (in fact, I prefer it), but I really want statsmodels to fix their implementation, and they're GPL-phobic.

Since Seaborn has boxplots, implementing an adjusted boxplot seems relevant.

edit: Oh, one more thing. I'd love any feedback on how to improve the "design spec", in case I wasn't able to make it clear enough.

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Are you really suggesting that it's not possible for you write an independent implementation of an algorithm from the version you once read? Is this sort of "clean room" approach typical? It strikes me as absurdly cautious.

Interesting dilemma. I had assumed that re-writing in another language basically meant you were copyright free (as long as you're not literally transcribing or automatically translating), but it appears it's not that simple: http://imranontech.com/2006/12/04/are-algorithms-copyrightab...

It is what is known to be legally safe. We do it all the time in GNU Octave, and we always tell people to not read Matlab source code when implementing Octave functions.

Besides, I just don't feel like it's fair to the R copyright authors. They worked hard to produce an implementation and they copylefted it, and I heavily relied on their implementation in order to reimplement it myself.

According to the United States Copyright Office[1], the algorithm itself can't be copyrighted, so that's why I wrote a high-level description of the algorithm.

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[1] "Copyright protection is not available for ideas, program logic, algorithms, systems, methods, concepts, or layouts."

http://www.copyright.gov/circs/circ61.pdf

I agree -- you shouldn't read sources you don't want to treat as derivative while you're writing an independent implementation. So yes, the code you've already written is GPL.

But suppose you decide to reimplement the algorithm now, months later (based only on the notes you wrote on Wikipedia). I'm not a lawyer, but I would say that's almost certainly independent, unless you have extraordinary memory.

I don't know. Maybe. I don't know how a judge and a jury would interpret that situation. They might agree with you or they might not. The only safe jurisprudence I know of is clean-room design, and it's what the SFLC documents I have received recommend.

That is a gorgeous Wikipedia article. Well-cited, easy to navigate, and just the right amount of mathematical detail.

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