There’s some community history, but the short version is that the US patent office issued Slice a patent for surgical tube in hot ends* which Slice has then used to litigate away competition. As a result, Slice’s actions have not sat particularly well with the parts of the 3d printing community that value open source and community innovation.

* there’s some debate as to the validity of that patent as there’s evidence that this idea dates back to the early reprap movement. Source.

Additional commentary

Given that the video is over a year old, nice to see that slice hasn’t tried to sue him out of existence.