What does this fix address?

The KF2 SDK workshop application crashing at startup in build 1057.

Where do the fixed files go?

Into \steamapps\common\killingfloor2\Binaries\, replacing the existing files.

What if the replacement does not help?

Restore the original files with Steam's verify and repair method and look for another solution.

KF2 SDK Workshop Tool Crash at Startup: Fix for Build 1057

A short community note for modders: the workshop tool that ships with the Killing Floor 2 SDK crashed at startup in build 1057. The author posted a replacement set of files.

What to do

Download the author's fix archive, named WorkshopToolFix1057 (a 7z file hosted on a file-sharing site; the original link was written with a space instead of a dot, so fix the address before opening it, and scan any download).
Copy the files with replacement into <Your Steam root folder>\steamapps\common\killingfloor2\Binaries\.

If it does not help

Restore the original files using Steam's file verification (the Steam support article on verifying game file integrity) and look for another solution.

Comments

One user could not reach the link; the author explained to replace the space between the host name and "com" with a dot.
Another user solved his own startup crash in a different way: disconnecting a PC game controller before launching made the game start. If you have a controller attached and the game or tool crashes at startup, try unplugging it.

FAQ

What does this fix address?: The KF2 SDK workshop application crashing at startup in build 1057.
Where do the fixed files go?: Into <Steam root>\steamapps\common\killingfloor2\Binaries\, replacing the existing files.
What if the replacement does not help?: Restore the original files with Steam's verify and repair method and look for another solution.