Atlassian JIRA
JIRA originated as an issue tracker, but has grown into very powerful tool used widely across the IT industry. SNOMED International started using JIRA to track software development projects, but it became clear that it would serve as an ideal platform to provide workflow and task management for the authoring and content request tools.
Only the minimum package, JIRA Core, is needed for the environment. A 30 trial period version is also available and can be downloaded from here - https://www.atlassian.com/software/jira/core/download
A key difference in the setup is to install this after Crowd and to then within the user directory settings, point the JIRA instance to use Crowd for user accounts.