Zanata have extensive api which you can use to gather stats:
To get a list of contributors over a period of time for a project version:
https://zanata.ci.cloudbees.com/job/zanata-api-site/site/zanata-common-ap...
To get the stats for a particular individual:
https://zanata.ci.cloudbees.com/job/zanata-api-site/site/zanata-common-ap...
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Alex Eng