Where can I find developer documentation?
Check out https://docs.dydx.exchange
Do you have API's for Market Data?
Subject to change, but you can try https://api.dydx.exchange/v1/markets which will update every few blocks.
Do you have API's for Depositing and Withdrawing?
Each deposit and withdraw requires sending a transaction to the blockchain from your own Ethereum wallet, so it doesn't really make sense for us to have a trading API. We can't sign your Ethereum transactions using your private keys, so you would have to send us the signed Ethereum transaction. At that point, it is not necessary for us to have it: you should just broadcast it to the network. You can, however, use the Typescript or Python libraries if you want to Deposit or Withdraw programatically.
Do you have API's for Placing Limit Orders?
Yes, see https://docs.dydx.exchange/#/api
Is there a TypeScript Library?
Please check out https://docs.dydx.exchange/#/typescript
Is there a Python Library?
Yes, it's targeted at automated traders. See https://docs.dydx.exchange/#/python
Is there documentation for the protocol?
Where do I report a security vulnerability?
Please see https://docs.dydx.exchange/#/security