Offline storage of data

Thanks for moving forward with this initiative. I believe that in this world full of developers and open platforms it can provide many interesting ideas and features for users, which are not/can not be done directly at Chess.com.

By reading README, I have one generic problem with the sentence below:

and by accessing these APIs you agree to not harvest or store the data for offline use in any way

I understand that you need to protect data and your know how, but if I would like to offer added value to users, then data has to be stored to some level. For example if I would like to provide additional statistics about club matches, that it is nonsence to call online full match history of the club online through API when manager send the request.

Please rediscuss this limitation.

Thanks. Petr

^Agreed. For example, if I use the APIs to access by own PGN games on chess.com, it would be strange if I could not save those on my own computer as this is currently possible via the website's UI.

Plus allowing storage means consumer of this API wouldn't have to hit the API when results are cached on local storage.

Not to mention that it seems unenforceable or undetectable. Maybe I'm just misunderstanding, but the way it is written today I read as "you can get JSON from the APIs, but don't save that JSON as a file".

Good points! We are working on clarifying. 

Thanks for the feedback, Petr and Pedro!

In this "first draft" of the data retention policy, I worded it very strictly because it is easier to permit more later than to restrict something after it is released. I appreciate the feedback. Once we have a better draft, we'll be sure to post it for comments.

Our main goals are pretty easy to understand:

1. We want our work on this API and your work on API clients to make chess more fun, interesting, and educational for the players here.
2. If you store the data and we have to change it (e.g., a player changes their username or avatar, a club team match changes the player roster due to membership changes, etc.), then the outdated data become confusing, and that's less fun.
3. There may be legal or ethical cases where we must restrict access to data that you previously had access to, and in these cases we need everyone to help correct things.

I have amended the README with this more detailed but still temporary statement:

All data are owned by Chess.com. This data retention statement is intended to provide guidance to developers as we gather their feedback and create a more formal agreement. The final published terms may change your rights, and by accessing the API you agree to apply those terms retroactively to data you may have previously downloaded. If you are not comfortable using an API and data which may have the terms of use change possibly frequently and without notice, then we advise that you postpone your development until after the beta period is complete. Please continue to participate in the discussion to help us craft the best policy for everyone.
Under no circumstances may data obtained from the Chess.com website or API be used to create or augment a competing service. If you are concerned that your service may be deemed "competing," ask us. Store only the data you need to provide your service and only for as long as needed. Respect the Chess.com community by not displaying or processing outdated and misleading data. Your rights to use, process, or share the data may change from time to time, so that we may protect our users' privacy and Chess.com's ability to provide an enjoyable service.