This is a great api for getting mobs into your game quickly!
If you have an idea for a mob, this will take care of all the basic function and also has some added functions to easily extend mob behavior! It is well maintained and reported bugs are squashed in a timely way!
this mod used to be great, the standard for mob frameworks a while back, however it has come to a point where it provides unnesscary overhead and lag while heavily limiting mod creators control over the mobs that they create. frankly the minetest lua api makes it easy enough to create a mob on bare metal with no overhead, or you can use mobkit, which still lets you retain nearly completely and low overhead as well as provides you with some sample behavior functions you can use
One of the few if not only existing author that takes their mods seriously to ensure critical bugs are fixed promptly. If your a serious server admin like me, you can't go wrong with their mods' collection and the fact that prompt support is normally provided to boot. :)