Replying to sbl:
gdal_translate with GRASS raster datasets as input worked, but gave warning:
Warning 1: GRASS warning: GISBASE enviroment variable was not set, using:
/usr/local/grass-7.0.svn
that's absolutely OK, it's just a warning that GDAL will use the version of GRASS which was used when building GDAL. If you want to use different version of GRASS, you can define it by GISBASE variable. Anyway this warning is probably misleading. The driver should probably check if GRASS_GISBASE exists on local machine and if not found than fail with error message: "Default GISBASE (%s) not found, you need to define GISBASE environmental variable which points to your GRASS installation". What do you think?