Dual Licensing Open Source: Can I Give Code Away and Still Sell It?
I want my code to be open source, because that is how developers find it and trust it. I also want to sell something.
I have assumed those two goals just coexist on their own. I have never checked whether a decision I already made quietly closed off the ability to do both.
How Does Dual Licensing Work?
Dual licensing means offering the same software under two licenses so different users can choose the terms that fit. The classic pairing is a Copyleft open-source license alongside a commercial license.
Users content to comply with the copyleft obligations, typically including releasing their own modifications, take the free version. Users who cannot accept those obligations, often companies embedding the code in proprietary products, pay for a commercial license that removes them.
What Makes It Possible?
Ownership. Only the copyright holder can offer software under multiple licenses. If you own all the code, you can license it however many ways you like. If contributors own parts of it, you can only offer what their licenses permit.
That is why dual licensing and the Contributor License Agreement (CLA) question are really the same conversation. Accepting outside contributions without a CLA and then planning to dual license is the most common way founders foreclose the model without realizing it.
What Is the Trade-off Nobody Mentions?
A strong copyleft license makes the commercial license valuable, because the obligations it lifts are ones many companies genuinely cannot accept. That same strength slows adoption, since some organizations will not touch copyleft code at all.
Choose a Permissive License instead and you maximize adoption while largely eliminating the reason anyone would pay you, because the permissive license already grants what they need.
The asymmetry to understand is that the decision reverses in one direction only. Code released permissively stays permissively licensed forever, and anyone may fork it from that point. A well-funded competitor forking your permissive core and building a hosted service on it is a normal outcome, not a surprising one.
Adjacent models are worth distinguishing. Open core keeps a functional core open and reserves features for a paid edition, which is a product boundary rather than a licensing one. Source-available licenses make code readable while restricting competitive use, and are commonly not considered open source under the established definitions.
Common Mistakes Founders Make
- Accepting contributions without a CLA. You cannot commercially license code you do not have the right to relicense.
- Choosing a permissive license and expecting to sell exceptions. The commercial license has value because it relieves obligations. A permissive license imposes few obligations to relieve.
- Describing a source-available license as open source. Whether a license meets the established open-source definitions is a factual question with a settled answer, and developer communities track it closely.
A Quick Founder Check
- Do we own or control rights in every line we would want to license commercially?
- Has a CLA been in place since the first outside contribution?
- Was our current license chosen deliberately, or inherited from a template?
- If we wanted to relicense next quarter, whose permission would we need?
- Do third-party components in our tree constrain how we can license the whole?
- Is the free-to-paid boundary a licensing line or a feature line?
- What would stop a competitor forking our code and offering it as a service?
The Bottom Line
Licensing strategy is one of the few decisions where the right time for advice is before the first commit is pushed, because publication itself is the irreversible act. Everything after that is working within what you already gave away.
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