In the aftermath of the devastating earthquake in Turkey and Syria, thousands of volunteer software developers have been using a crucial Twitter tool to comb the platform for calls for help — including people posting their location inside collapsed buildings — and connect people with rescue organizations to help them. But they could soon lose access to this tool unless they pay Twitter a monthly fee of at least $100 — prohibitive for many volunteers and nonprofits. Monday is the extended deadline Twitter set for shutting off free access to its API, or Application Programming Interface. But on Monday, it delayed the launch again.