The main reason Starmaker Story stays free is that it’s not the primary project. Kal’s main priority (and what the rest of the Arvus Games team is focused on) is Roundscape Eclipse, which is the paid title. Starmaker is a solo side project Kal makes in his spare time. It exists to fill the gap while people wait for Roundscape, and it also doubles as a useful sandbox where he can test Unity features and mechanics that might later get carried over into the main game.
Starmaker itself is planned to wrap up in two more content releases (1.9 and 2.0, not counting the Steam version). Throwing money at it right now and bringing extra people onto the team would actually slow things down more than help, because of the onboarding and training time required.
If the Steam release does well, there’s a possibility of a Starmaker spin-off about six months later, but it’s equally possible Kal might decide to revisit an Arenus remake or jump into something completely different instead.
Any proper funded/expanded version of Starmaker would have to wait until Roundscape Eclipse is finished (Act 1 this year, then two more Acts after that). By that point the community (and Kal) might want something else entirely.