Yes ACFS is not supported on HP-UX still, but you can install RAC and configure ASM. The options you have is install RAC with ASM.
>>Is it meant that ASM cluster FS is not certified on HPUX platform, and need to go by 3rd party certified cluster FS, before I can install the RAC DB ?
You dont need to install any 3rd party cluster, just install oracle CRS and configure ASM. There are plenty of documents but you can have a look at this doc http://docs.oracle.com/cd/E11882_01/install.112/e24615.pdf