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On any attempt to run i got the dialog:
“Blackwell” is damaged and can’t be opened. You should move it to the Trash.
Mac OSX 10.10.1 (14B25).

Verified on 2 machines: MBP 2011 and MBA2013
This question / problem has been solved by triockimage

Game "is damaged and can't be opened. You should move it to the Trash."
a) Redownload the game using the newest version of the GOG Downloader:
To download, make sure the " Downloader mode" is switched to ON before clicking the "Game installer" button. After the download is complete, reinstall the game.
b) Use this workaround if using the Download didn't help:
- Go to Applications -> Terminal
- Type in:
xattr -d
but don't press Enter.
- Drag the application to the Terminal window, this should add the path.
- Press Enter.