opengeo/gxp — pull request #152 by ChristianKreuzberger (2012-08-31 13:17:20+00:00)
Title: Print support for TMS and Vector layers "enabled" in Print.js

added TMS and Vector as valid printable layers to plugins/Print.js

at about Line 241:
function isPrintable(layer) {
return layer.getVisibility() === true && (
layer instanceof OpenLayers.Layer.WMS ||
layer instanceof OpenLayers.Layer.OSM ||
layer instanceof OpenLayers.Layer.TMS ||
layer instanceof OpenLayers.Layer.Vector
);
}

Yes, I think those layers should be supported, and I just tried them out with Mapfish-print they work fine!
Geoserver has issues with them because they are not using the latest mapfish-print plugin. It crashes because of this (for TMS):
https://github.com/mapfish/mapfish-print/commit/2cee3210800e51495619272935f39c14cecafb7a