Have you ever considered open-sourcing SLT? This is your only route to immortalize this amazing piece of software. I'm sure you'd receive immense community contributions and widespread support. If you switch to a donation model + enterprise support plans, I think you're likely to earn greatly more than you currently do.
I love SLT and have used it throughout my career, but I still feel more comfortable depending on Atom because I know it will be supported by the community in the event that something bad happens with the ownership. If you don't open-source SLT, I sadly believe that open alternatives like Atom will outlive it.