I second the Dungeon Tile group on Yahoo. I use their sets and Pymapper, a DT program, to plan my encounters, then I take poster tack ("Monkey Snot," Scrib) and affix them to black poster board (22"x30"). If I need a larger area, I use multiple poster boards. This has really sped up use of Dungeon Tiles, since I no longer need to pull them out of a bag and set them up during play.
While it could definatley be a grey area. As long as they don't include scans of the DnD tiles there's no reason they couldn't. People (with more articstic ability than I have) could easily make their own tiles to share (with those like me looking for an easy tool to make printable maps).
PyMapper can print the dungeon to a single page, or across a range of pages (ie, 4 wide by 3 high). Poster size prints can be made as well.
The limiting factor is the quality (resolution) of the tiles. Generally the tiles are in the 80-150 ppi resolution range. Good for the screen, not so much for 1:1 printing. Custom made tile images with much better resolution can be used if you have them.