Symptoms

Need to change form runtime url from https to http
 

Diagnoses

Switching the K2 site configuration to use HTTP instead of HTTPS would require the K2 environment to reconfigure to use HTTP. There is a couple things that you would need to be aware:
1) If you have any custom ASP.NET project that makes use of the K2 environment variables (i.e. Smartforms runtime/viewflow url, web service url). Then those solutions would not work and would need to be fixed and redeployed.
2) If SharePoint environment is setup to use (HTTPS with SSL) and the environment is integrated with K2 through K2 for SharePoint App, when switching K2 sites to HTTP, K2 for SharePoint components will not work. As per the documentation, K2 and SP in mixed-mode will not be supported, see link below:

http://help.k2.com/onlinehelp/K2ForSharePoint/ICG/current/default.htm_Install_Topics/Before/Topologies.htm?TocPath=Overview%20and%20Architecture%20of%20K2%20for%20SharePoint|_____2
 

Resolution

If the above doesn’t apply then you should be able to re-configure K2 site to support HTTP (this can be done by configuring the bindings for HTTP and then rerunning both the "K2 Blackpearl Setup Manager" and the "K2 Smartforms Setup Manager" and selecting the appropriate http "Bindings" to be used by default.