Some things about this make me doubt ...
1) no mention of pay worth a js genius
2) they want the person to do html, css and js!?! ... yet this is supposed to be big ... and they can't even hire separate people for html/css and js
3) no mention of what the project is about
4) no mention of any company
So they are looking for an _unemployed_ js genius for an unspecified period and the pay probably isn't too good. Plus the company is probably 3 people including you and will be bankrupt before you finish your job.
I'd like to say "Sounds good to me, I'm in." but unfortunately I don't qualify as a js genius, I don't live in England and I would seriously need alot more information if I was a js genius.