Yes, indeed it is true, I have given access to thierry4wd so he can finish developing firmware for S17e. It works as it should, in my case I was interested in underclocking due to ridiculous hot days that we have during the summer (and that we will have over next years - thank you very much global warming).
I will not be posting too long review here as I have already written a full one which you can check at bottom of my post.
This is the first S17e firmware that is legit and that I am aware of on this forum and in general. I am happy to see that people are taking after some other firmware creators and accepting one-time payment as method of selling their firmware (I do not personally like firmwares with fee since I use my machines for long time and that costs much more than if it was one-time payment).
However, as I am not currently aware of the price I cannot say if it is worth it or not, but I think he will not overprice it like some people do.
I cannot vouch that there is no malware or backdoor built-in but I highly doubt that there is one as mikeywith and Biffa vouched for this person (check the thread below for that too).
As of writing this post, my miner has been working around 48h non-stop (even though we just hit 43 C today in my city) while underclocked (whereas before I (or rather "he") installed his firmware on my machine, I couldn't run it at all due to outside temperature and machine always reaching 90 C and turning it self off or dropping to 0TH/s to protect itself).
Before upgrading to this firmware you will have to sd-card flash MPTest firmware like many other firmware since Bitmain locked most of their newer devices and does not allow you to flash just any firmware whenever you want. But I assume that he would send you a tutorial or explain you what you have to do when you buy the firmware.
His English is not the best as you can see but he is trying his best and really cares about machines and customers (or at least that is what I gathered from talking for almost a week with him).
I sincerely hope he will become one of big custom firmware developers as we URGENTLY need competition in these waters.
Oh... I said it won't be a long post.. Ah well, I tried my best to make it short.
You can see my full review here:
https://bitcointalksearch.org/topic/m.54891215.