From When is open sourcing a threat to business?:

The short answer to "when is open sourcing a threat to business" is that it is a threat when it allows competitors an easier and cheaper path into the market.

If so, then why aren't open-core or dual-license easier and cheaper paths for competitors to enter the market? Even when the real money makers for a business are not in the core but in the non-free add-ons, isn't it still easier and cheaper for competitors to only build the add-ons than having to build both the core and the add-ons? Let's say A is the original company and B is the competitor. B can compete by:

  • making its own add-ons, or
  • packaging the core with its own add-on and release in a different brand

Why does A let B do that?

  • 2
    Sorry, are you asking why if A releases a product as open-core, B doesn't move in and corner the market in proprietary add-ons?
    – MadHatter
    Commented Nov 29, 2023 at 16:25
  • B packages the core of A's product with its own add-on and release in a different name
    – Ooker
    Commented Nov 29, 2023 at 17:29
  • you mean what AWS does with databases? Commented Nov 29, 2023 at 19:05
  • @planetmaker what does it do with databases?
    – Ooker
    Commented Nov 30, 2023 at 2:04

1 Answer 1


Alice builds from scratch and releases her own open-core product. You ask why Bob doesn't either (a) make his own proprietary add-ons, or (b) copy her code and release it as Bob's Open Core, with Bob's proprietary add-ons. The answer in both cases is that Bob may not do that.

Alice will have released her core under a copyleft licence, probably GPL or AGPL. It is generally understood that plugins for a GPL program must themselves be GPL. Yes, this can depend on how the plugins communicate with the open-core, but you may rely on the plugin architecture being designed in such a way that plugins do have to be GPL - or the open-core model doesn't work. So - unlike Alice, who isn't bound by her own licence grant - Bob's plugins must be GPL.

Even if Bob takes the open-core code, modifies it, and releases it as Bob's Open Core, Alice still has a copyright interest in it, so Bob is bound by the GPL, and still cannot release proprietary plugins.

  • 1
    what if Bob doesn't release his core, but package with his own feature and release the whole as closed source? How do Alice or other people prove that Bob take her code?
    – Ooker
    Commented Nov 30, 2023 at 10:51
  • 1
    GPL enforcement is a whole different question, and is not limited to open-core models, but applies to anything copyleft. I'm not saying it's a bad question, but it's not this question - at least, not as written.
    – MadHatter
    Commented Nov 30, 2023 at 11:07
  • @Ooker: That question is off-topic on this site since it has nothing to do with Open Source. The exact same question arises when someone copies closed-source code. For example, if you take the source code of Windows, do a search&replace and sell it under the name "Doors", how does Microsoft prove that you took their code? It's the exact same problem, nothing to do with Open Source. Commented Dec 9, 2023 at 22:10
  • 1
    @JörgWMittag then which side would it be on-topic? And why is asking about GPL enforcement not about open source?
    – Ooker
    Commented Dec 10, 2023 at 2:57

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