developers who contribute.
Maybe terminology matters.
There are 2 kind of contributors.
1) People who are part of the core team (of either FPC or Lazarus). Those people can themself commit to the SVN.
2) People who contribute (contribution range from small changes, to entire new features)
Within the Lazarus/FPC community the former (1) are often called: Developers.
The latter: Contributors.
Developers can be found by getting an svn log, and extract the committer, then "sort | uniq -c".
If you want to filter by "recent active", then restrict the log to the time frame of interest.
Contributors for Lazarus are listed in the IDE, and the file docs/contributors.
However there is no easy way to distinguish between, the size of those contributions.
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The Lazarus git mirror lists over 40 names that committed. Not all of them are currently active. (I would guess maybe half of them)