From the github contributors list I noticed that on selecting a range between 2009-2010 I can see few developers https://github.com/bitcoin/bitcoin/graphs/contributors?from=2009-08-30&to=2010-12-31&type=c and https://github.com/non-github-bitcoin (an account created for commits before the bitcoin-core code was probably migrated to github from sourceforge)

1) Satoshi Nakamoto
2) sirius-m (Martti Malmi)
3) laszloh - based on some commits made here https://sourceforge.net/p/bitcoin/code/252/log/?path= (go to older and you'll find them all here) https://sourceforge.net/p/bitcoin/code/123/
4) Gavin Andresen

Leaving this video here for fun too: https://www.youtube.com/watch?v=DjYbsq3FXfM (It shows a visualization from 2008 - 2018 all the developers involved based on commits made)