  We report activity data analysis on several open source software projects,
focusing on time between modifications and on the number of files modified at
once. Both have fat-tailed distributions, long-term memory, and display
systematic non-trivial cross-correlations, suggesting that quiet periods are
followed by cascading modifications. In addition the maturity of a software
project can be measured from the exponent of the distribution of
inter-modification time. Finally, the dynamics of a single file displays
ageing, the average rate of modifications decaying as a function of time
following a power-law.
