Sometimes developers pull their own apps. I have no idea what this one was, so I can't comment on any reason why it might have disappeared. But I haven't seen Roku pull a channel themselves that only could be used with illegal sources. As you mentioned, that could end up being a number of different channels, even their own Roku Media Player, since that can use playlists to connect to many online sites that might not be legal.
Nvidia Shield, Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.