At what point can I call GPL code my code? [closed]

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I need some legal advice if possible.

So I'm going to be implementing some code under OSS license. I realize that even if I rewrote the implementation, I need to include the license.

However a lot of sources that I use to learn are under GPL Licenses. So even if I take what I learned and implemented it in my own way and heavily modified the code, with the only similarities being logic flow, I still can't claim the work as my own?

What about algorithms that are extremely proficient? (Like binary Heaps) Do I need to include the inventor of the binary heap into my code?

Also, as I understand it from GPL, if I use the code, even modified, does this mean I need to release the all of my code that even associates with it? So if I make a whole application in a closed system and I plan to sell it, I still have to release all my code via OSS license?

Let me know if I need to provide more information about my question, thanks.

Answer 1

The license on a given piece of software is only relevant if you are using that particular piece of software (or a part of it, or a version of it you've modified yourself, or a part of it that you've modified, etc). If you write an equivalent piece of software yourself, completely 100% from scratch, then there is no license on it until you choose one yourself.

What you appear to be worried about are software patents, not licenses. The GPL doesn't let you sue someone for writing code that uses a similar algorithm or UI elements (assuming you didn't actually use any GPL'd code in your re-implementation), but patents do. And a lot of real software companies have ludicrously broad patents that may or may not hold up in court, if only to act as a defense when other companies try to sue them with their own patents.

If you need actual legal advice on how big of a risk this is for your project, you definitely need to consult a lawyer. Patents are hard. If you're just curious, then you may find it interesting to read about some high-profile "clean room reimplementations" such as Google's Dalvik VM for Java, which Oracle attempted to sue for patent infringement but lost. I would also guess that the people/companies who publish GPL'd code in the first place are probably not the kind of people/companies who sue others over software patents, but of course there's no guarantee.