While @MadHatter 's answer make sense, @Tiny Lincon is correct. I had a chat with TinyMCE's team meanwhile and their response is as following

It is mandatory to show the branding when using the open source version of Tiny and would require a commercial contract to remove it.

Note that, this is true for community cloud as well as community self-hosted.

P.S. Using it is free, it is that you will need to show branding (recommended way is to show in footer/statusbar of editor itself or anywhere else visible in page)

While @MadHatter 's answer make sense (and should be accepted and I think is correct), @TinyLincoln is correctly reporting TinyMCE's interpretation of the LGPL. I had a chat with TinyMCE's team meanwhile and their response is as following

It is mandatory to show the branding when using the open source version of Tiny and would require a commercial contract to remove it.

Note that, this is true for community cloud as well as community self-hosted.

P.S. Using it is free, it is that you will need to show branding (recommended way is to show in footer/statusbar of editor itself or anywhere else visible in page)