I have not tested this idea, but I think that a good rule for inclusion (in the Megabundle) is that someone who is a fan and not a dev is willing to write a description.
For example, I could write a description for: Ragnarok, ADOM, Crawl, IVAN, PRIME, Drakefire Chasm, Larn, Spelunky, ChessRogue, Jeff Lait's 7DRL pack (I have some kind of dev contribution to three of these games, but I think this is not important)
Probably the subbundle including TOME would also have to include notable roguelikes using the engine?...