When an administrator wants to expose tlwebaccess through a reverse proxy, on a given URL that's not / (say https://host/custom/), they need to rewrite all URL:s that's passed through the reverse proxy rather than just rewriting the hostnames. If we'd offer the possibility to prepend a custom path to the tlwebaccess URL:s, we would make it easier for administrators to configure their reverse proxy. In other words, with a url prefix of "/custom", make tlwebaccess serve pages on /custom/main and /custom/websocket, rather than /main and /websocket.
*** This bug has been marked as a duplicate of bug 5394 ***