Dave, you can have multilayer board in free version of Eagle and even generate your Gerbers!
Eagle's CAM Processor complains about layer configuration but produces correct output files.
The policy about 3rd party files is something along the lines of that a loaded file is not a subjest for editing restrictions.
Fun fact: one can add additional layers to a standard 2-layer board and use them with little effort for power planes even in restricted freeware mode.
1) Open XML board file in text editor and declare new layers by copying and editing layer definition lines;
2) Open edited board file in Eagle, add a top/bottom polygon and then change layer that this polygon belongs to (you can do this multiple times back and forth);
Editing these layers is still prohibited, so it is not possible to put regular traces there, but one can have complex polygons correctly connected to vias and TH pads