What's the current api call limit for free plan?

The "don't have any API limits at all" claim you quoted was not posted by a Dropbox employee and is not accurate.

1. The Dropbox API does have a general rate limiting system that applies to all account types, including free accounts, but we don't have any specific numbers documented for that. It is relatively generous though and the limits operate on a per app-user basis. If you do hit the general limits, the wait period is usually only on the scale of seconds to minutes anyway.

Also note that not all 429s and 503s indicate explicit rate limiting, but in any case that you get a 429 or 503 the best practice is to retry the request, respecting the Retry-After header if given in the response, or using an exponential back-off, if not. I recommend reading the error documentation and Error Handling Guide for more information.

2. Yes, there is an additional specific limit for upload calls to some Dropbox Business team plans, which is now "1 billion API calls/month" for "data transport" noted here. This is a limit on the number of upload API calls that can be made per team per month, for certain Dropbox Business team plans only.

3. This only applies to upload calls, and not other types of calls. You can find more information on this limit in the developer documentation here.