Is it possible to flash htc desire on linux (drivers concern)?
Yes. It is possible to flash android devices under linux. The fact is that Android does not need drivers - both adb and fastboot use libusb and talk to the devices directly. Your main concern should be finding compatible fastboot binary - some OEMs use proprietary fastboot extensions to handle certain functions.

Obviously you can not expect to be able to follow the windows tutorial under linux. Fortunately for you unrevoked (the tool used in the tutorial you linked) has a linux version as well.