I've written yet another unofficial GOG downloader. It's written in Lua but relies on wget for all the heavy lifting (including download resuming). I expect it will work on any Unix-like system wtih Lua and wget available. It's under the MIT license. Sample usage to download all The Longest Journey setup files and extra might be:

gogdl login
gogdl getlist
gogdl download @the_longest_journey-all

First gogdl prompts you for your username and pass. This is cached locally so you'll only need to do it until the cookie expires. The second command tells it to retrieve your games list on your account page and extract the available setup files and extras (again, this is stored in $HOME/.gogdl and only needs to be occasionally refreshed as you buy new games). Finally we download all setup files and extras from TLJ.

Get gogdl at Github where there's a full README. If you're happy with one of the existing alternatives there's probably not much to tempt you away, just thought I'd share. Any comments/questions/bug reports/patches! are very welcome.

I've pushed some changes. It's now possible to do gogdl check @the_longest_journey-all to verify that all setup files and extras are present and your local filesize matches the remote. For setup files you can go even further - I now support downloading the xml checksum files used by the new official GOG downloader. e.g. gogdl download @the_longest_journey-checksums will download setup_tlj.exe.xml. You can then verify the md5sum of your downloaded setup file by doing gogdl checksum setup_tlj.exe.xml. See the updated README on the project github page for full details.

Any bugs/questions/feature requests just let me know.