Someone from Humble Bundle Inc. got back to me.

They re-added the Linux DRM-free download and Jazzpunk-Oct-30-2017-Linux.zip now shows up in both my Humble Indie Bundle 13 purchase page and my unified Humble Library view.

I downloaded and extracted it and all of the stuff in Jazzpunk_Data has a modification date of 2017-09-28 21:09 as well as a few of the other files, so I'm assuming that's when they had Unity do the build.

It also contains level19 through level26 and sharedassests20.assets through sharedassets27.assets files not present in my older installed copy, as well as some PS4-related Mono DLLs, so I'm assuming this is indeed the Director's Cut.

It also drops the 64-bit executable for some reason (the old build had 32-bit and 64-bit ones) but I have so many 32-bit-only games that I'm not going to make a big deal of it and mouselook smoothness seems improved over the older version.

Given the date and the content, I think this is a case where a relaxed version of Hanlon's razor applies. (Never attribute to malice what can adequately be explained by stupidity/incompetence/laziness.)

Whoa! I checked my library and see same thing. Great news! Its quite strange, ofc, that they did it just now, like 3 weeks since actual Directors Cut update. Interesting thing is that Humble Store still says Director's Cut is provided via Steam key for Windows, Mac, and Linux and is also provided DRM-Free for Windows and Mac.

My money's on incompetence. The build having been made for three weeks but not uploaded could have various explanations... but coupled with allowing a period where the old build has been taken down but the new one not put up?

(The Humble Store is a red herring. There are a TON of games that had a DRM-free Linux version in a Humble Bundle but don't offer it for Humble Store purchasers. I believe they're separate licensing contracts.)

I have some very crazy suspicion that maybe we both have it added back because we actually complained to Humble. Now that we need is to check is folk who didnt complained got it too?
Can you please check is Jazzpunk magically returned to your Library or not?, because both i and ssokolow received updated linux jazzpunk build in ours.

I just asked among my circle of friends and one of them confirmed that the "new version posted 2017-11-21" copy is in his Humble Indie Bundle 13 purchase page too.

There's a Linux build from 2017-11-21 in my library too now.

Yep, I've got an updated Linux build of Jazzpunk as well. And it must be the Director's Cut since it's 1.2GB while the previous one was like 500 or 600MB.

Well done, guys! :)

Yeah, only thing i miss now is Nexus DLC which is doesn't seems to be coming on Humble, albeit, for example, Race the sun have its Sunrise DLC here.
And GOG does not allow to purchase DLC without base game owned.

More good news for Linux users! Earthworm Jim 1 & 2 have now Linux support:

Having played EWJ 1 during high school, I never knew that a Dos port existed.

There was also a Windows 95 port of the Sega CD version with the CD soundtrack and extra level.

I tracked down a copy and have been meaning to play it (either in Wine on my main Linux machine or on my P133 retro-gaming PC with Win98SE).

And here it is! :)

If only it was part of the sale!

The sale isn't over yet. ;)

And even if it doesn't make it, there'll be other sales before the year ends, so fingers crossed!

While we still wait for Corpse Party and The Coma: Recut, here's another possible incoming Linux build:
https://www.gamingonlinux.com/articles/battle-chef-brigade-combines-combo-based-hunting-and-puzzle-based-cooking-its-on-linux.10763