hMod was the original and most popular Minecraft Server mod for Minecraft Alpha. Hmod added a few features to Minecraft, but more importantly, allowed the creation of plugins to be loaded and change how Minecraft worked. It was created by hey0, and later a team of developers. Hey0 eventually lost interest which made it hard for the team of developers to further develop hMod. Official releases had to wait for hey0 as well.
Many of the original team of developers for hMod then went to create their own project called bukkit, so that they could make things the way they wanted and felt were needed. The introduction of bukkit was received with mix feelings. Many welcomed the promise of many improvements to hMod, but some felt the sensational titles about hMod's "death" from team members like sk89q was unprofessional. It got worse when hMod was unexpectedly dropped completely, shortly after bukkit's introduction. This left players with no server mods at all due to bukkit still being at a very early stage in development. When bukkit finally had a working version, it was missing many features people were used to using. This and a few other things caused a split between modding communities. One side supporting bukkit, and the other hMod.
Despite the claims of its coming "death", hMod was continued by Meaglin, and eventually a team formed and called themselves Canary. Even though Canary had a different name, they continued developing with the original hMod code, and made sure it was known that they were just using a different name. With this, hMod is still continued, but under a new name.