I am not familiar with the details of any of Larian's contracts, but I would assume that since GOG always creates their own patches, that developers for new releases can not bypass that process. I have not followed the patch process for any other new games on GOG.
I don't think there is anything illegal, though, about giving the patch to anyone else (presumably nobody with issues then would contact GOG support for something they hadn't officially released yet).
I would assume the downside of making patches more freely available was people contacting support after trying to install the wrong or an unnecessary patch (which could be limited by better error messages), and the added complexity of testing new patches. Or maybe most people just expect to get updates where they got the game, or something.
I used
Hash to create some checksum values for the patch (which installed fine here).
File: DCPatch1_0_33.exe
Size: 70124488 bytes
File Version:
Modified: August-16-13, 7:46:34 PM
MD5: 8F896EBDDB5CBA4FB75A17705E1E7B74
SHA1: 68966F18E7F9722DA61BC4D76A240B00B87C1718
CRC32: BB76A9AA