I, being a company or individual, can:
- Download and use the compiled NetBeans IDE for free,
- Download and use NetBeans' source code for free, and
- Modify NetBeans source code and redistribute it for free (or for sale) so long as I follow the terms of the SPL, including the following provisions:
- I must bundle the SPL with any source code version I distribute,
- I must make my changes to the NetBeans source code available back to the NetBeans community under the SPL (so the community can benefit from my changes),
- I cannot modify the the rights granted under the SPL License,
- I must duplicate the notice in Exhibit A of the SPL found at http://www.netbeans.org/about/legal/spl.html in each source code file, and I must generally follow all the other requirements of the SPL.
- I can add external files to NetBeans, compile these and redistribute them for free or for sale and I do not need to make such external files or changes to them available in source code form or binary form to the NetBeans project (if my value-add is worth the price - I can sell it) .
The NetBeans source code is meant to be open source and freely available. You can distribute NetBeans for free or for sale. However your version needs to contain proper attribution to the authors (so your version still shows who wrote it). If you modify the NetBeans source code files, those modifications need to be made available back to NetBeans Community with proper notice of the changes as called for by the SPL (that's what we get out of it). Files which you write entirely by yourself and add to the IDE do not need to be made available back to the NetBeans Community.
Source: NetBeans User FAQ