Something I have found of with the Isogenric Engine, which I have been considering due to the networking capability. But there is a catch... there is a 2% royalty involved. Which to me is not a deal breaker, but unfortunately the 2% royal extends past the transactions of the software, if I had read it right.
That is, essentially if one's IP generates income, even with out-of-game transactions, such as selling of t-shirts from an external web site, that income will also have the 2% royalty applied. That to me is a deal breaker.
Excerpt:
IE: "Works" is the IP
Royalty fees are charged against revenue generated regardless of the source or destination of a transaction so long as the revenue is related to the Works.
Transactions that are related to the Works will be defined as but not limited to: in-game advertising, on-page advertising, in-game transactions, on-page transactions, currency conversion transactions, purchases of digital and real-world goods and merchandise, marketing goods, mobile device transactions, in-game currency transactions, any transactions that originate, terminate or pass through the Works.
Licensee agrees that all transactions that are in any way related to the Works are subject to royalty fees.
For simple games that are not expect to generate much income, still not a problem, but if ever want to expand on the IP or use other streams of income, such as merchandise or sponsorships...
And there is no cap on the royalty... I'll see if I get response about this from the developer.