Morphs are a bad way to rotate things. Stick with yRotate. If you saved as cr2, rather than crz, you can text edit the file to change the name on the dial of the rotateY channel to "Open", eg:

                rotateY yrot
                        {
                        name <span style="color:rgb(255,0,0);">Open</span>

You may want to hide the other rotate and translate channels, and force limits to zero, so the door can't be moved in undesirable ways, eg: rotateZ zrot { name side-side initValue 0 hidden 1 forceLimits 1 min 0 max 0