There is no restriction. That is the point. You are saying that If I cannot mine an idea for my personal profit by restricting others from using what I write even as I use what they have written, that is restricting my freedom to use that software. That is a very twisted idea of freedom.
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Way to cherrypick a phrase out of context!
I don’t care to debate the merits of the GPL. This isn’t the forum for it.
Bottom line: If OP releases the software under the GPL, there is a bunch of us [very experienced, very skilled, software engineers] who won’t touch it beyond generic use; won’t debug, won’t contribute patches, won’t work on it exactly because it is under the GPL.
There is always the simple option of releasing any code under a GPL compatible license such as MIT or Apache at which point it could be used in a GPL library.
There will always be developers that won’t patch or submit changes for a variety of reasons. The main point is that there are many successful GPL projects that didn’t need those developers in the first place.
Regardless it’s been interesting to hear another side of the debate, I’ve always been one to pick the best option for that moment in time and the future goals for a project.
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And many others like my very experienced, and very skilled, surgeon Grandfather who have advanced humanity while still managing to earn a good living at their main job. The merit (or lack of it) comes from suggesting that everyone else think as you do about licensing and leave it available for you to exploit and restrict others from using your work. suggesting the least toxic ideas are the most toxic,
i.e. Not about GPL but about “toxic”
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GPL is toxic and restricts freedom when used. If I use something that has GPL license in my project that has other code that is not GPL licensed, then the other code in my project has become infected with GPL. I lose the choice over how my code can be handled. So my choice is either use the GPL thing and give up my freedom, or not use the GPL thing.
If it was just about changes/additions to the existing GPL’d code, then fine, but I could have hundreds of thousands of lines of code that is not GPL’d, and if I use a few lines of GPL code as part of that, it’s all now considered a derivative work of the GPL’d code. That’s BS.
THAT is the problem with GPL for most coders.
I use MIT license whenever I can for my own code that I release. I do use some things that are GPL licensed (Qt for example) and those projects are generally kept carefully segregated from anything I don’t want infected (which is almost everything).
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It is interesting POV, and you have a point where a small bit causes the larger set to become GPL, For the programming I did, I started out modifying other code for efficiency as my first PC computer had a maximum size LISP that it would load, and that was a good teaching tool as well, but later I would just look at the goal or approach and do that myself usually more elegantly due to my starting point, but while there were a few I had not bothered to do more than update to the latest Autocad quirk everything I had I had written, though several were modifications of what I had written before.
When I was paid to write I had to make sure in the contract that I continued to have rights to use my own code which was usually something I had to fight for, so my experience was different.
One last question, What are you using to generate the pulse for the stepper drivers? As in, are you using a PRU (How beaglebone does it)/FPGA? Or Atmel of some kind? Or direcly from the Linux instance?
The problem with your argument here is that for one reason or the another you “chose” to use someone else’s work when you were “free” to do otherwise. It appears that people feel their “freedom” is being restricted because they want to use and modify software they didn’t write for free (without paying), this also seems to imply they aren’t skilled enough to write it themselves in a reasonable timeframe. GPL allows one to pay the creator for a license that grants them perpetual use without “infecting” their work.
You are also “free” to build a similar library and release it under its own license. The real issue throughout the argument seems to be that people “feel” they lose their freedom when someone else the “creator” of GPL’d code wants their work, time, and freedoms to be respected.
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For the prototype, I am planning on generating them from the Linux instance (PREEMPT_RT extended) to keep it simple.
I realize this is not ideal, and intend to move over to a hardware based solution in future revisions (this is just an early prototype). I have not yet decided what that solution will be.
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@scott.wiederhold Have you thought about a name for your board and/or any modified Glowforges? I’m thinking “LightForge, The AfterGlow” 
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Wow, really? You read my post and that is your answer?
I guess I should have expected that. I’m done with this debate here.
I’ve migrated the repos to Github:
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It’s alive…and kicking!
In the video, it is running the program from this setup:
More details are on the project site.
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Outstanding work. For all those worried about GF closing up shop and leaving us a brick, this should settle their minds. I can’t wait to see what you do with creating/enabling advanced features that GF hasn’t been able to do. Or what they’ll come out with now that it’s not a closed system 
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Awesome stuff… also those stepper drivers are the devil. TMC2100 series are so much better for noise!
Those are TMC2130’s you are hearing - with StealthChop engaged!
This video is the same program, but letting the TMC2130’s interpolate to 256 microsteps from Glowforge’s standard 8:
Noticeable difference…
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Hmm… still quite loud. I’m running a DuetWiFi board for my 3D printers. Uses the TMC2660 drivers, with the right settings I ended up with nearly silent stepper noise. The fans are louder than the motors. I’m thinking that it might just be the driver current settings or the way the PULS is done? Either way I’m sure some tweaking can be done to quieten those down even further.
In my set up I tweaked the currents to as low as possible. Such that I’m not skipping steps and the torque is enough to drive everything. If I remember correctly, my settings are no more than 80% of max for my usage case.
But the important thing is that you’ve got the thing moving about 
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I haven’t started the tweaking yet…
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I’m eagerly awaiting the PEW PEW part of testing 
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Bear in mind that the GF puls files are 10kHz samples of the step waveform. So when step rate is not at exact subdivision of 10kHz, which in general it isn’t, then the reconstituted step waveform is not regular. I.e. at full speed it alternates between 2 ticks and 3 ticks between steps at a sort of beat frequency. I don’t think the TMC2660 will be able to interpolate that smoothly as it can’t know what the next period will be.