Google last year said, that YouTube no longer requires a Google+ profile to upload, comment, or create a channel—today, a new custom URL system unifies your identity across YouTube and works independently from Google+ is launched.
Currently, Google has two system in place to claim a custom URL, "you can either choose a YouTube generated format: youtube.com/ChannelName," or, "youtube.com/c/ChannelName — that's generated by a system integrated with Google+."
With these two formats in place, users are requesting similiar URLs with similar names, but in these two different formats. So, to avoid duplicating channel names in the future, the new system launches today will "now point both URLs from the older systems to the same channel." This means, "users can now reach the same channel with either youtube.com/ChannelName or youtube.com/c/ChannelName," Google said.
This also means that claiming a new YouTube custom URL does not involve a custom URL for your Google+ profile, and vice versa.
Further, they note, that while this is a positive change for millions of channels with custom URLs, however, less than 0.02% of channels with custom URLs will need to reclaim a URL due to duplication conflicts.
Google said, this effected group will be notified to claim a brand new custom URL, "from the channel's advanced account settings until May 31, 2017 to make this change."