It requires a license (https://code.jsoftware.com/wiki/Jd/License#License).
> Non-commercial use is free.
Do you mean that not only the DB has to be open source, but it also should be free-as-in-beer?
A few companies manage to get people to pay for tools (e.g. Unity, Visual Studio), but they're the exception, and it's more due to a lack of open source offerings with comparable features.
No one would pay a license for a new JS framework or for a compiler outside of niches, which is where proprietary tools still survive.
If you want mass adoption, you need a complete free offering (as in beer and as in freedom). Which sucks for the tool vendors, since that's a lot harder to monetize, if not impossible.
On the other hand, it's a boon for people getting started since they can try out all these tools without a monetary investement, and it's great for companies who don't need to pay for the code they base their whole business on.