The Evening Standard's report on his signing implies that there is an option to buy, without explicitly saying so:
" The 24-year-old Morocco international (right) has agreed a season-long loan which could turn into a permanent move from Championship side Queens Park Rangers if he impresses manager Martin Jol."
Source: http://www.standard.co.uk/sport/football/adel-taarabt-i-couldnt-say-no-to-fulham-8749959.html
Footnote: They are the only paper I've been able to find which comments, one way or the other on the 'option to buy'
" The 24-year-old Morocco international (right) has agreed a season-long loan which could turn into a permanent move from Championship side Queens Park Rangers if he impresses manager Martin Jol."
Source: http://www.standard.co.uk/sport/football/adel-taarabt-i-couldnt-say-no-to-fulham-8749959.html
Footnote: They are the only paper I've been able to find which comments, one way or the other on the 'option to buy'