This layout makes all accented characters used in Danish, Dutch, Finnish, French, German, Italian, Norwegian, Portuguese, Spanish and Swedish available through one AltGr keystroke.
The Mac implementation was forked from EurKEY Keyboard layout, which features a QWERTY baseline layout (=good access to braces etc.) with quick access to commonly used accented characters and Umlauts, changing the AltGr key sets to match weur's proposal.
Status: New version built from Ukelele, should match almost all the keys from the original layout
If using Homebrew, there is a Cask for you:
brew install tjsousa/cask/altgr-weur
If you want to install manually or just for your user, follow the instructions below:
Copy the two files altgr-weur.keylayout and altgr-weur.icns to your library, either system-wide (/Library/Keyboard Layouts) or for your local user (~/Library/Keyboard Layouts). A system-wide installation is preferred though to ensure the layout is available to all applications. (See also this Superuser answer.)
Open your keyboard preferences in System Preferences > Keyboard > Input Sources, click the + button on the bottom left side and select AltGr WEur under Others:
The Layout itself is licensed under GPLv3. The EU flag icon is taken from Iconspedia, created by Alpak and licensed under CC