I believe that coding style in a project is important thing. MySQL, PostgreSQL, Linux and FreeBSD kernels, glibc and many other excelent open source projects have their own coding style. The styles are different and that's expected because they were developed by different people with different preferences. The only crucial thing is code consistency. I guess you saw a code where spaces and tabs were mixed for indentations - it is always disgusting to work with such code. So the code of a project can use any style his owner likes which, but it must be consistent.
In our projects we follow Linux kernel coding style (you can find it at linux/Documentation/CodingStyle) with some additions for C++. We use the same coding style for kernel C and application C++ programming, so we have adjusted the original guide with some C++ specific things. Here it is.