Cycles is available under the Apache license, but the version integrated into Blender is licensed under the GPL just like the rest of Blender, so I don’t believe this can provide an exception/excuse in this case (I am not a lawyer though). Just to remind people of a couple relevant bits of the Blender Foundation and GPL licenses:
“You are hereby granted permission to copy and distribute the Software
without written agreement from BF. This entire License Agreement, and
the GPL-license.txt must appear in and/or accompany all copies of the
Software. The source code distribution, which can be found at the same
location where you obtained the Software, has to accompany all copies
of the Software as well.”
“For example, if you distribute copies of such a program, whether
gratis or for a fee, you must give the recipients all the rights that
you have. You must make sure that they, too, receive or can get the
source code. And you must show them these terms so they know their
So while the GPL does not care if you charge money for the software, it does require that you make the full source code available along with any binary distribution, and that you are giving up all proprietary rights to any changes that you make as soon as you distribute those changes to someone under the GPL. Every person who acquires a copy of the program has the right to redistribute it without restriction as long as they comply with the requirements of the GPL.
The GPL promotes a software development environment which operates like a “co-op”, where everyone contributes a little because they want to share in the results. This is just like a group of farmers getting together to buy one combine harvester for $1M and then sharing it during the harvesting season. It works great because none of those farmers are in the combine harvester sales or manufacturing business. Of course the sales people at John Deere hate this idea because they believe that every farmer ought to be buying their own $1M piece of equipment from them.
In the software world this co-op development method works great for something like Blender where many of the people who want to use it also have the ability to contribute to it, perhaps writing an add-on etc., or maybe they just contribute money to support paid developers, and everyone gets the value of everyone else’s work. This is because like the farmers, the majority of people working with Blender are 3D artists, not professional software developers, and they don’t ordinarily make their living writing software like blender, just as none of the farmers are in the combine harvester business. Thus the key is that the people contributing to the project are doing so with activities that are not their normal profession.
Where it does not work so well is where a company tries to get the benefits of open source while simultaneously trying to make money selling something that’s actually free. A good example is RedHat, who “sell” RedHat Enterprise Linux even though it’s covered by the GPL. This leads to some weird corporate neuroses where they try their best to make you think you must pay them to get access to the product, and many customers are used to paying for things like this so it works. But just try to find a page on the RedHat site that tells you Linux is actually free software and that you could get the same distribution from CentOS for free. CentOS is even owned by RedHat now.
In the Blender world, there are many people selling add-ons for Blender which are covered by the GPL due to the way they’re integrated into Blender using the Blender APIs. For the most part this works fine, because people don’t mind rewarding the authors for their work, even though the GPL actually encourages people to share software and you might think that only one copy of each GPL add-on would ever be sold because the person who bought it would just share it with everyone on the internet.
At some point though if you’re trying to pretend that you have your own proprietary special product that’s really just an enhanced Blender, and that the community norms and software license don’t apply to you, and you try to charge a lot of money for your special version, you may find that some people will be unhappy about this because they perceive that you’re not playing by the community rules. And the GPL will make it very difficult to make money in a traditional fashion if people don’t voluntarily choose to go along with it.
Lots of people have contributed vast amounts of time (many without any direct compensation) to produce the platform that you’re building on, and they contributed their efforts because they wanted to see Blender get better, and in most cases because their main motivation was so that they themselves could have access to that better Blender. This is one of the most magical things about Blender as a project, that the “co-op” model applies so well to it.
I think everyone is really excited about the improved Cycles performance and the potential of getting these benefits in the official Blender distributions.