FreeRTOS was previously GPLv2 with a couple of added clauses (anything linked with FreeRTOS is now GPL too and you can't publish performance metrics without approval). I'd imagine there were a lot of companies not wanting to GPL everything they made with FreeRTOS (i.e. Amazon) so with a new MIT license, anyone can do whatever they want.
> As a special exception, the copyright holder of FreeRTOS gives you permission to link FreeRTOS with independent modules that communicate with FreeRTOS solely through the FreeRTOS API interface, regardless of the license terms of these independent modules, and to copy and distribute the resulting combined work under terms of your choice
It was GPL with an exception that allowed you link your app code to the OS, with your app becoming GPL.
>you can't publish performance metrics without approval
Curious to know if anything knows if that's actually enforceable. The GPL gives you permission to use an distribute a program and code. I can see where if you got your copy straight from RTOS, they can enforce that clause. But, to me, the GPL seems to give everyone the right to distribute the source without that clause. And it seems to explicitly forbid the addition of additional licensing terms:
You may not impose any further
restrictions on the recipients' exercise of the rights granted herein
And there is nothing stopping you from taking the original GPL'd FreeRTOS codebase and merging in all of the MIT licensed improvements. If you make a better FreeRTOS, that's what people will use.
I've seen this happen many times in open source. For example, to this day LGPL's LibreOffice, which started as a fork of OpenOffice, reviews all OpenOffice patches and cherry picks the good ones.[1] On the other hand, Apache OpenOffice can't benefit from any of LibreOffice's patches.
Viral licenses like GPL have an edge and will win out if there is a community that actually cares.
GPL licenses tend to discourage adoption due to their onerous restrictions, which is why most projects today choose anything other than the GPL family of licenses.
The virality of GPL actually results in most companies explicitly banning the use of GPL tools and code to prevent the GPL from "infecting" their own code.
For what it's worth, LibreOffice is probably LGPL because of OpenOffice's history with the Oracle buy-out. Oracle gave OpenOffice to Apache for the same reason Google gave Wave to Apache: They run a sort-of paliative service for software projects.
Their "fork" is additional libraries for FreeRTOS specifically for IoT kind of stuff packaged into the kernel. Not everyone needs an Amazon version of the FreeRTOS and most users wouldn't want extra junk in the kernel considering the kind of hardware that an RTOS is meant to be run on.
