Yes, both GitHub and NimbleWork offer a Free Trial.
GitHub is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
NimbleWork is designed for Large Enterprises, Medium Business and Small Business.
Pricing for GitHub Starts at $4/User/Month whereas for NimbleWork Starts at $10/user/month.
Some top alternatives to GitHub includes LiveCode, Codeanywhere, Visual Studio IDE, CodeinCloud, GitLive, Microsoft Azure, GitLab, CodeSee and Bitbucket.
Some top alternatives to NimbleWork includes Quickbase , Smartsheet, ClickUp and Zoho Projects.