I've got a question about author rights and open source software.

Assuming I want to build a software. A similar software is already created, but isn't free at all and owned by a company. Can a build an open source clone of the proprietary software from scratch? Or is it forbidden by intellectual property?

And what if I use proprietary ideas in the open source software?

  • 4
    Open source alternatives to proprietary software get made all the time. What could bite you are software patents.
    – Doval
    Aug 8, 2014 at 13:36
  • AFAIK, in Europe, APIs or DSL specifications cannot be protected by patents or copyrights (some upper European court trial). GIYF Aug 9, 2014 at 6:51
  • You don't say what country you are in which would help, not everyone is american! (Tho to get a good answer you are always going to have to consult a lawyer)
    – James
    Aug 9, 2014 at 7:45
  • 4
    I'm voting to close this question as off-topic because it is asking for legal advice.
    – user22815
    Jan 6, 2016 at 0:20

2 Answers 2


You are certainly permitted to build compatible software and there is nothing in Copyright Law that prevents you from doing so. Ideas cannot be protected, only their expression in a particular software 'work'.

The same is not true of Patent Law. This protects an 'invention' and you cannot use a patented invention in anything without permission of the patent holder.

You should bear in mind that there could be considerable financial risk in doing this. Companies that have invested money in developing software are often prepared to invest money in lawyers to protect it, and finding out whether they are right or not can be very expensive.

The odd thing is: if you try and fail, they'll probably leave you alone. The greatest risk comes when you succeed.

If you head down this path then sooner or later you will need competent legal advice, and that also costs money. By all means give it a go, but be aware of the risks.

You might have thought that releasing the source code or even making it public domain would protect you, but it does not. Any legal action would be about the damage you did to a company by your actions and releasing the source code might even aggravate the situation.

  • And what if the open source code is send into the public domain (Unlicense for example) ? Is it always possible to have problems with companies ?
    – Moktuss
    Aug 8, 2014 at 14:06
  • @Moktuss Yes. When anyone can convince a court that any of your actions violates their rights in some way, you will have to pay reparations. It doesn't matter if you actually benefit from doing so. Preventing them from convincing a court will require you to pay a lawyer representing your side of the story.
    – Philipp
    Aug 8, 2014 at 14:11
  • @Moktuss: Agreed. See edit.
    – david.pfx
    Aug 9, 2014 at 0:42

'Proprietary ideas' the bizarre concept that it is, is often covered by patent law.
You can however clone to your hearts content. Bear in mind that clones sufficiently close in appearance can land you in legal hot water. The sufficiency of that is determined by the pursuant, the judge, and/or the jury.

One thing that is important, you can not use any assets that you do not have a right to use. Assets include sound and graphics.
You may also be hit with a cease and desist. These are about as friendly as it gets. They ask you to stop or they will pursue legal claims. Sometimes these C&D orders have a good standing, other times they are threats on shaky ground.

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