I just installed gcc and use openocd to program.
I'm fairly sure I just did "sudo apt-get install gcc-arm-none-eabi" for the compiler.
http://libopencm3.org/wiki/Main_Page is worth looking at too, in case you haven't seen it.
Come on, there's a lot of 'just' there. It's not too bad if you just want to play with the discovery board, but there's very little documentation on how to use the discovery board as a programmer. The official docs for the discovery board don't give you crucial information about jumper settings, and I ended up having to download some bloated Windows tool from STM just to output a suitable .ld script for the STM32F030K6. I'm sure it's not as difficult as it used to be, but it's vastly less straightforward than setting up an AVR toolchain.
To be honest, the page you linked to contains no useful information. I can see that it's some kind of peripheral library. It doesn't look like it does anything in particular that StdPeriph doesn't already do (and 90% of example code uses StdPeripg). Plus the github page warns that the API is unstable. Again, compare to AVR. The arm tools are much better of course, but it's so much harder for a beginner to find answers to simple questions. E.g., can I reset an STM32F0K6 with only two pins using OpenOCD and the STLink programmer on the discovery board? (The answer appears to be yes, but it's not readily googleable.)