Let's hope that the "modern rewrite" doesn't slow it down too much ;)
On topic - kudos for being free. There must be a threshold where a company that's "free forever" can be thought of as being there for the long haul, and I think 15 years definitely cuts it!
They are telling me for years to make a paid plan and that was always the idea. Maybe it's 15th birthday is good for that too.
With all due respect, you probably should plan around this. What if you suddenly die tomorrow? I'm not trying to threaten or scare you, its just that you (and your customers) should plan around this. An example of such planning which likely fits the glove for all readers here, is to have your private key or password at a notary.
It's ok, I did do this; like said above, the source (and all keys/access) are in escrow at a notary for the projects I run in case of bus-hitting. Also, I am not working alone, but yes, I will rethink this again as it was a while ago that this was arranged.