give them your steam id and password lol

Originally posted by htfcmcghee:

give them your steam id and password lol

XD starting to look like the only way

Well, you can't edit the same level at the same time but you can transfer the local map file. They are located in [SystemDrive:]\Users\[UserName]\AppData\LocalLow\Blacklight Interactive\Golf With Your Friends\CustomLevels - AppDate might be a hidden folder in Windows by default, check your view settings if you can't find it.

Also only the user that initially published the map should push any updates, while I'm not 100% on this but if you try to publish a file with an existing ID it will change it in the level file and publish a 2nd version with that new ID. In case that happens go in with a editor (personally I go for a hex editor because it doesn't change anything else when saving) and change the ID back to the one from the workshop url (.../sharedfiles/filedetails/?id=1234567890) - just make sure to close the file in the editor as the level editor refuses to open files that are opened in another program at the same time.

Like he said, a lot of workshop maps you can just transfer the map file to do so.
Appdata is hidden.
by doing %appdata% in your windows search will unlock for view and follow what he said above.
It's a bit annoying, but shouldn't be too hard to share.
Hopefully steam could add (at some point), moderator access to workshop files.
If not that would be abused in some cases.