Complex sentence: The Linux kernel has used the merge window process since July 2005 with the release of version 2.6.14, since then, every 2.6.x release has been followed by a two-week merge window.
Split into simpler sentences: The Linux kernel has used the merge window process since July 2005 with the release of version 2.6.14. Since then, every 2.6.x release has been followed by a two-week merge window.