I can't comment on the dev activity for any of these tools, but I do have experience with lab.js and require.js. From what I have seen, the functionality of he

I can't comment on the dev activity for any of these tools, but I do have experience with lab.js and require.js. From what I have seen, the functionality of head.js looks like a subset of lab.js. Lab.js has a richer API with queueing and waiting. Require.js is a whole different beast - it revolves around the definition of modules (module pattern) and the scripts required to pull down to organize modules. There are a lot of tools in require.js that help with ordering the execution of loaded scripts, pulling down files as text (can't do this in lab.js), and optimizing (compiling modules into one big uglified file). They are all good tools, but different - pick the best one suited for your project.