You can use Max’s own built-in OSL Map shader node with appleseed materials, for instance as a procedural texture node for the appleseedDisney shader (see screenshot).
For this to work you have to enable
Use Max Procedural Mapsin the
System section of the render settings.
These are the good news. Now, the bad news is then you won’t be able to use the newer appleseeed OSL materials, only the appleseed built-in ones, and you won’t be able to export the scene to an appleseed project file.
Obviously this is not a good solution. To fix this Max procedurals would need to be re-implemented in OSL and added to the current appleseed shader family, similar as it is done in appleseed-Maya.