sltoo is a free and open source requirements management tool. It is a fork of rmtoo.
sltoo uses a different approach than most other requirements management tools: it comes as a command line tool which is optimized for handling requirements. The power of sltoo lies in the fact that the development environment can handle the input and output files - there is no need for a special tool set environment.
Example: if you need to handle baselines (and there often is), sltoo can be configured using a revision control system, e.g., git. The revision control system can handle different revisions, baselining, tagging, branching and many other things extremely well - there is no reason to reinvent the wheel and making it less efficient.
Let one thing do one thing.
See the release notes for the release history.