How much of the Steam cataöog is owned by big publishers? 10%? These generate most of the revenue. Bit there is this incredibly long tail of smaller games ownes by small publishers and indies who self-publish. These are virtually exclusively Unity engine titles. And there is no way any of thesw could afford the 6 or 7 digits for a source license. And unless thungs changed, you won't even considered eligible without an exceptional track record.