The idea is to make this a commercial product, to sponsor the development of a game I'm working on with my colleague.
I'm playing with the idea of having a free or trial version, albeit non-source and probably somehow limited if only through licensing restrictions (ie only for truly free apps). The source version will definitely have a paid license.
I've also been looking into Patreon, though I'm a little wary of the unclear situation regarding VAT. But if they get that figured out, I'd love to set it up so that eventually reaching a given price point would allow me to make more and more of TK available for free while leaving some features exclusive to Patrons.
For reference: At this point Patreon essentially has its VAT-collecting (for-profit, not VAT exempt) EU customers like me (but not Bjørn) inadvertently commit tax fraud because they don't even give you enough information to collect the VAT yourself - not to mention how time consuming and costly that would be. But once they get this sorted out, I'll start uhm ... patreonizing.