Hello there. I'm considering using an open source rendering engine as part of a game engine I wish to develop. The engine is the Geometric Tools Engine and it uses the Boost License. The engine can be found here: http://geometrictools.com. I will need to modify the rendering engine over time and make improvements. Therefore my rendering engine will be a derivative work. I am unclear about a few things when it comes to licensing. GPL requires any program using GPL code to include the copyright notice at the top of all source files and also with any binaries when the derived program is distributed. However, the Boost License is a lot less restrictive. A copy of the license does not have to be included with the executable of the derived software but must be included in the source file when the code is distributed. It also states that any code distributed alongside code covered by the license is not subject to the license's requirements. This brings me to my first question:

Assuming I want to fork the rendering engine and keep it private (which the license permits), can I also add my own copyright notice under a different license to source files in the modified engine that I add? So if I create a new class and I modify an existing class from the original code to link to it, can that new class still have my copyright under a different license? I assume the code I add to the original class cannot be licensed differently.

My second question is related to leaked code:

Let's say I set up a company and develop software derived from software covered by the Boost License and an employee leaks the derived code. Seeing as the derived code is also covered by the Boost License, can anyone obtaining the leaked code legally use it for their own purposes? Even though it may be covered by an open source license, it was not the intention of the author for the code to be distributed.

Thanks for any answers or suggestions.

1) Assuming I want to fork the rendering engine and keep it private (which the license permits), can I also add my own copyright notice under a different license to source files in the modified engine that I add? So if I create a new class and I modify an existing class from the original code to link to it, can that new class still have my copyright under a different license? I assume the code I add to the original class cannot be licensed differently.

2) Let's say I set up a company and develop software derived from software covered by the Boost License and an employee leaks the derived code. Seeing as the derived code is also covered by the Boost License, can anyone obtaining the leaked code legally use it for their own purposes? Even though it may be covered by an open source license, it was not the intention of the author for the code to be distributed.

1. The original code is covered under the original license, so you must do what the license says about including their license verbatim, with at least one blank line above and below the license as required. You can use either the long form or short form, as described in the Boost FAQ. If you add additions to the file it becomes of mixed authorship and things get a little more complicated. You should include your name as a contributor and copyright holder to a portion of the file. Exactly the wording you want to use is up to you and your lawyer. I've seen quite a few variations of "Portions of this file are copyright foomatic, inc, 1994-2014" and similar.

2. Boost license is not viral. There is no requirement that your changes be licensed under the same terms. As you control the copyright you have several legal options. Perhaps the easiest is a public plea of avoidance on your web site where content is released, a notice that "On {date} we were informed of a defective version released by someone. Please be certain you download the products directly from us. We are not disclosing their name or website so we don't inadvertently promote them. Contact us if you need additional details." Other options involve leveraging the legal system, which may not be worth persuing if you, the leaker, or the unauthorized receiver do not have much money. Leaked secrets may be worth a discussion with a lawyer depending on the value (either to you or to them) of what was taken.

Thanks a lot for the response. Really appreciate it. It seems then that there really is no disadvantage to using code released under the Boost License because if you edit it, you can include your own copyright for the additions. Does it have to be specified in the copyright on top of the file what lines of code have been modified or added?