Today's Deal of the Day is Cepheus Deluxe, which draws its core from the Mongoose Traveller OGL. From what I've seen, the Cepheus Engine is widely supported and is compatible with much of the Traveller material available.
Until tomorrow morning at 11 AM Eastern, Cepheus Deluxe is on sale, marked down to 4 bucks from 9.99.
Cepheus Deluxe is a set of rules for playing classic science fiction games. It includes rules on creating characters, resolving actions, fighting other creatures, and engaging in space battles, generating worlds, handling the risks of interstellar speculative trading, exploring new worlds, and many other activities. While designed for fast, action-packed play rather than an accurate simulation of reality, Cepheus Deluxe encompasses a wide variety of rules and materials for building a science-fiction universe and playing in it.
Cepheus Deluxe draws its inspiration from old-school science-fiction roleplaying games. It shares many similarities with these games. Material from older rules sets and those created with Cepheus Deluxe, the old Cepheus Light, the Cepheus Engine Core, and old-school sci-fi roleplaying games, are easily compatible with only a moderate amount of adjustment.