I'm guessing it was intentional. This is the first time I've seen it called "khamas," but what I understand from looking it up is that it's how the word is commonly written/pronounced in english in Israel. (If I'm wrong, please correct me!)
Fair enough. And I should be clear, I didn't find a good source for this explanation, all that came up that was related was a few forum threads. And now that I'm looking at it again, there's a good variety of completely different answers out there. So I really don't know what to believe here.
I may just not be searching well; if anybody does have reliable info about this I'd be happy to hear it :)
It's the standard transcription of the Arabic sound, which is closest (in fact, pretty much identical) to the Hebrew sound which is typically used to pronounce the first consonant in Hamas. Blame the bad Arabic-language education is Israel for not pronouncing it correctly...
This is, as far as I know, not a word in Arabic, and non-standard transcription for Hebrew — the standard would be "Ḥamas" or "H̲amas" (using "ch" is common but non-standard as well).