TDF has been announced on September 28, 2010. At the time, developers focusing on the LibreOffice source code were a rather small number. According to Ohloh, in August 2010 hackers committing code were 41 for OOo and 50 for LibreOffice. Let’s assume then that LibreOffice hackers were just 9.
I remember that several people pointed out immediately that the number of TDF developers was not adequate for the size and the scope of the project, and set the minimum at 25. I suspect that they were far too quick in expressing their judgement.
In fact, the 9 TDF hackers were left alone just for a few hours.
Between September 28, 2010, and September 30, 2010, 21 new developers joined the group (source of all numbers: Ohloh). In October 2010, new hackers were 86.
The growth has never stopped. In fact, at the end of December 2011, the cumulative number of new LibreOffice developers was an astounding 379 (the image does not need additional comments).
Most of these hackers are volunteers, who donate their skills and their time to the project. Of course, most of them cannot contribute on a daily basis, although they are all doing wonders.
Combining old and new developers, TDF hackers have always been at least twice as many as the minimum set at 25 (again, the image does not need additional comments).
A quick final note to explain the sharp drop between March and April 2011. On April 15, 2011, Oracle announced that it was going to stop the development of OOo (unfortunately, the original press release is no longer available).
As a consequence, Oracle developers – whose contributions, merged by TDF developers, were duly counted – disappered almost immediately.
The situation is easier to understand from the following histogram, which compares the number of LibreOffice and OOo committers since September 2010. Data for OOo are those extracted from Apache OOo, which has replaced OOo at Ohloh.
I am quite amazed by the tiny number of Apache OOo developers since August 2011, although someone has tried to explain me – a recognized tech illiterate – that hackers are counted in a different way, and only a subset shows in Ohloh numbers.