This challenge started as a private joke, dating around 2005. Without any hint it is too hard to solve, since you need to know personnal things about Greg. Here I'm going to tell you a few things about the guy:

• He's a (brilliant, of course) mathematician, who worked in the Toulouse math dept from 19XX to 20XX and now is in Grenoble, see his Web Page.
• He proved a famous identity: McShane's identity (GIYF).
• He has quite a personality. He loved riding his bicycle when he was upset, which resulted him reaching an almost professionnal level of training.
• He used to advocate the programming language called Python. In fact, he showed me a riddle website, The Python Challenge, which I liked very much. I decided to write a parody of this website and to dedicate it to him :)
• He is also a tech afficionado, and definitely an Apple guy.

Well… with this info the riddles should be accessible to a much wider audience. Still… many of them require geek knowledge and/or math knowledge (of varying levels).

More hints?

• No solutions require capitals.
• Number 3 needs a little bit of hacking.
• Number 6 is the one that needs most advanced math, ask an expert if needed!
• The few sentences in French are easy to translate, but for the lazy people, I included translations thereof, somewhere.
• Ever heard of HTML?
• How much do you know about PNG?

Btw, do you know this interesting website: The genealogy project?

Note for hackers: None of the riddles' solutions involves a web attack, none requires knowledge about the many internet protocols, no need to send strange requests to the server :) All the material is already given to you, for each riddle.