However, if you modify NetBeans source code files, you must make them available to the NetBeans community and satisfy the other terms of the SPL. In general, for any file covered by the SPL which you modified for your product, you should:
- include the notice form found at http://www.netbeans.org/about/os/license.htmlin each file,
- retain the modified file and (preferably) the diff from the NetBeans version,
- make these patches publicly available as source code preferably by uploading them to contrib.NetBeans.org so they will be publicly archived on netbeans.org, and otherwise comply with all other applicable terms of the SPL.
Source: NetBeans User FAQ