Yes, both GitHub and Userback offer a Free Trial.
GitHub is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Userback is designed for Individuals, Freelancers, Medium Business and Small Business.
Pricing for GitHub Starts at $4/User/Month whereas for Userback Starts at $14/Month when Billed Yearly.
Some top alternatives to GitHub includes LiveCode, Codeanywhere, Visual Studio IDE, CodeinCloud, GitLive, Microsoft Azure, GitLab, CodeSee and Bitbucket.
Some top alternatives to Userback includes Backlogs, Backlog, ReportBugz, Buglog, Usersnap, Ybug, Bug-Track.com, Disbug, Feedback Monkey and Toybox.