> 17. Reject if transaction fee (defined as sum of input values minus sum of output values) would be too low to get into an empty block
Last I saw 0 transaction fees are allowed. Is this correct as a minimum?
There is no network enforced minimum fee (though it must not be negative). Individual miners can choose their own minimum fees, however.
Also, is COINBASE_MATURITY still = 100 ?
Yes, the network enforced value is 100.
What's the best place to find the current value of these magic numbers and get notified when they change? I've been able to google some of them in the official client code on github, but was just curious.
Thanks for the help!
A lot of the values you asked about will likely not be changed for a while, if ever, as most of them would be changes that fork the blockchain (something the main bitcoin developers go to great lengths to avoid). I think the best places to find this information is probably the wiki and the source code, otherwise just asking people in the forum or in irc.