KDBUS is the in-kernel implementation of D-BUS, which is a core interprocess communication architecture used to build the GUI in every desktop Linux system today. Putting this code in the kernel provides performance improvements, as well as fixing many limitations that cannot be overcome by userspace-only code. After quite a few years of development, it looked like KDBUS was finally ready for merging into the Linux 4.1 kernel. However, controversy has now erupted. It seems from a look at few of the comments that they are objecting, not to the implementation, but to the protocol, which cannot be changed, otherwise it is no longer a drop-in replacement for D-BUS. <http://www.phoronix.com/scan.php?page=news_item&px=KDBUS-Taking-Heat>