Client belongs to somneone else than Bluebyte/Ubisoft, you should adress all issues to them. Unity is what they aimed for and with all its backfires BB accepts client as a third party solution wich will last - my guess - till they get Unity up and running 100% (more than a year later).
Its not illegal, but its untill further notice accepted because they cannot fix their own issues on Unity. Wich they would have known was a theme if they just had googled Unity before signing any agreements :-)