The serial from gog works on the WUBE website. Alas, the serial is only displayed when visiting GOG.com, not from the client on your PC!
(select game from library on website, more, third option "Serial Keys")


Thx, finally i had to buy the DLC in the web, becaouse Gog didn't allow me to buy ...

Hi, in the factorio web page says:

"Purchases from our website or GOG can redeem a free expansion Steam key.
If you purchase on Steam, you can link your Steam ID to our website to access the non-Steam downloads."

But it doesn't say how to obtain the Steam key if i buy the expansion from GoG ...