Yes, both GitHub and Celoxis offer a Free Trial.
GitHub is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Celoxis is designed for Large Enterprises, Medium Business and Small Business.
Pricing for GitHub Starts at $4/User/Month whereas for Celoxis Starts at $25/month when yearly.
Some top alternatives to GitHub includes LiveCode, Codeanywhere, Visual Studio IDE, CodeinCloud, GitLive, Microsoft Azure, GitLab, CodeSee and Bitbucket.
Some top alternatives to Celoxis includes Quickbase , Smartsheet, ClickUp, Zoho Projects, Jira, Basecamp, Microsoft PPM, Wrike, monday.com, Asana, Teamwork, ProjectManager.com, Microsoft Project, Quick Base, Resource Management by Smartsheet and Height.