Yes, I'd thought of non-wall usage of masks, and I think the opportunities are tremendous. Forget about just providing a "replacement" for Dundjinni, this could conceivably eclipse DJ. And I hope that doesn't come across as pretentious or boastful. I just see so much possibility here! Masks are essentially just very precisely-defined brushes and stamps, if you think about it. Blending different textures together, like where grass meets a road, can be achieved fairly realistically with very little effort on the part of the user, if a good mask is provided.
I hadn't given much thought to how elevation changes will be marked, but I suppose using semi-transparent overlays over a base texture might do the trick.
As for Linux, unfortunately my development environment won't compile native code for that platform. MapForge should run under Wine and using Virtualbox, but I know that's not ideal.
Bummer about Linux, but I understand(I have a Windows XP on Virtualbox, so hopefully it would work in that and if not, then WINE would at least be a suitable alternative(and I have Windows 7 on another partition, but it's a PITA to reboot just to use a windows instance.)
I don't know how much in depth knowledge you have with GIMP or PS, but if you have any questions, feel free to PM me here or on CG.
Another thing I just thought of (one RobA put into his dungeon Script plugin for GIMP), would be a displacement filter for a mask. To explain, make a selection or mask and the displacement would make it a bit more fractalized using a cloud layer for the randomization. The idea here is for making an excavated room with slightly non rectangle/circular/etc walls. Of course, you could achieve some other means of fractalizing a mask shape. Example image with a BIT of the effect: https://www.cartographersguild.com/atta ... 1234485936
and the explanation of how it was done in GIMP : https://www.cartographersguild.com/show ... #post66947
I can say, the more options that would replace GIMP functionality, the more likely I might get behind and and purchase MapForge.