Short explanation taken from https://crystice.com/jack/:
It supports Quake 3 Arena, too. I'm a little bit hyped to see another editor using BSP and all that jazz in these times and age, but apparently it's for sale on Steam for EUR 15.00? Really? I'm not sure how to think about that but I fear that people will simply stick to their old editors instead of paying money for a more recent one given that these kind of editors are not exactly industry standard anymore. :dork:J.A.C.K. (formerly known as Jackhammer) is a brand new level editor for games with a quake-style BSP architecture. The title stands for “Just another creation kit”, but actually it’s not just another level editor! The aim is to develop a convenient cross-platform tool capable of incorporating the best features of existing editors, such as Valve Hammer Editor, Q3Radiant and others.
What does everyone else think about this? Has someone probably already done some work in that editor?
PS: Just saw that there's a free non-steam version available as well (Non-Steam J.A.C.K. version 1.1.1064), that makes it more interesting for me at least! And the most recent version it seems is from 2016, so I'm a bit late to the party, still I haven't heard of J.A.C.K. until now.