Yes, as said "In fact, go 1.16 has reverted to using this as the default now. The memory graph after this change looks much better and steady at 2G.". Upgrading is definitely next, not easy though since Google appengine flex still does not supported 1.16 out of the box https://cloud.google.com/appengine/docs/flexible/go/runtime
We do not plan to make money out of it right now. If we reach a scale where we cannot sustain it off our pockets, it would be easy to raise money for it.
Right now we don't see any obvious scalability bottlenecks. The one problem we see right now is the user has to enter info about him (which we call iotas). Going further, we would like to automate this process as much as possible.