Transaction fees: https://en.bitcoin.it/wiki/Controlled_supply. Mining is subject to market forces and they can switch off/join anytime. I recommend this book if you want a deep dive — the draft is free: http://bitcoinbook.cs.princeton.edu/ A lot of theoretical discussion but it will be interesting to see how it plays out empirically when we reach the cap.

You can spin your own node but most of the big players today (i.e pools) are people you can find and chat with at a conference. Similarly, anyone can do a pull request (https://github.com/bitcoin/bitcoin) but practically all of the top contributors to the code-base are familiar faces either in developer circles or academia. There is almost nothing strictly anonymous on bitcoin itself. On a public ledger at most you are pseudonymous.

The p2p ledger space is also evolving. Some competing implementations do away with hard supply caps. Others play with the inflation rate. Some even do away with mining all together (see Casper/staking) or are meant to track resources (solar energy, rendering time…etc).