ThinLinc is designed to run with reference SELinux policy and users in the unconfined context. It is possible to use ThinLinc with other policies and more restricted contexts, but will most likely require modifications to your policy to accommodate ThinLinc.
The local system policy will optionally be modified by tl-setup during installation. The SELinux module and other policy changes performed can be examined in /opt/thinlinc/share/selinux. Execute the command /opt/thinlinc/share/selinux/install to reapply ThinLinc's policy changes.
The ThinLinc policy module is distributed in source form and therefore requires the reference policy build environment. On Red Hat based systems this is always installed, but other systems might require extra packages.