hello,
does the Mac launcher work for you?
mine downloads the patcher every time i start it but then it doesn't patch anything.
it creates a Patcher.zip and Patcher in the game folder.
i've tried to chmod +x the Patcher without extension and when i start it it asks for a KSP store email and password; since i don't have such credentials i don't know what to do.
i've also tried to download and install the 1.1.3 version from the gog download page but it doesn't work, my game version is always stuck at 1.2.6
how could i update the game to the latest version?
thanks.

I think the launcher is intended for the direct download version of the game only rather than the GOG or Steam versions. That was not always the case, but I think that's how it works now. If I try to force the launcher to run on my Windows install it doesn't work there either.

The GOG version is only updatable using downloads from your GOG library or with Galaxy. If you can't get the updated installer to run, then I think you need to contact GOG support.