Is it possible to authenticate with client service libraries via ClientLogin? There are only OAuth2 examples in Google Code but it requires unneeded manipulations.
ClientLogin is deprecated and should not be used. It also doesn't work with newer APIs like the Tasks API.
Sorry but the answer is no. While it may seem more complicated at first, using OAuth 2.0 and NOT storing passwords yourself is ultimately a much simpler and safer solution.
https://developers.google.com/google-apps/tasks/auth
Jay