The original (mostly) estonian team that used to work out of a re-converted house/wharehouse building, there were a bunch of them, so it depends on what you measure ''original'' as; Kurvitz, Rostov and Hindpere are notoriously touted as THE original core team (understandably so, Disco Elysium was born out of a setting they had come up with for a TTRPG campaign almost 15 years prior).

They were apparently fired after they had discovered a scheme by Toni Haavel and Ilmar Kompus (allegedly with help of Kaur Kender) to pipeline money out of the funds for a side-project and straight into buying up a majority of shares in the company, effectively wrestling out the ownership of both the IP and the ZA/UM corporation (not to be confused with the ZA/UM artist collective, founded by Martin Luiga, which was disbanded for semi-unrelated reasons after his apparent internment in a psychiatric facility).

But Kurvitz's core team weren't the only ones that contributed to bringing Disco Elysium to life; Argo Tuulik, Dora Klindzic and Justin Keenan, by example, remained in the company for quite some time after the ownership legal fiasco had happened, with Argo himself even being interviewed in the infamously biased People Make Games docu-report, this would later lead to a ''humiliation campaign'' by the managers in ZA/UM targetting Tuulik, resulting in his demotion and subsequent firing from the company.

the last bunch of original developers that had contributed to Disco Elysium were either fired along with Tuulik during company re-structuring events or had already left the company beforehand. If im correct, Summer Eternal seems to be made up of this last wave of original devs, since it does not include any of the aforementioned Core Writers. SE also seems to be the only ''successor company'' to actually proudly announce the amount of original devs it actually has, unlike Longdue and Dark Math who constantly parade two or three graphics and environment designers as proof of their legitimacy as ZA/UM successors or something