Who controls the source code?

Who has commit access to github source? Is the project open source?

Why your zcash ideas cannot be implemented as sidechains on bitcoin? If they can, what will happen with zcash?

Yes, the project code is open source: GitHub - Electric-Coin-Company/dev-ci-zcash: dev-ci testing using zcash clone, synced with github.com/zcash/zcash

Who has commit access is an operational and security issue; it’s currently restricted to Zcash employees. You’re welcome to fork the github repo and submit pull requests, although note that our review processes are quite strict.