A statement like:

  "It lies 168,000 light years (987 quadrillion miles) away ..., which means that at the time of the explosion, woolly mammoths still roamed Europe ...."

is highly misleading in the framework of Special Relativity: There is no universally agreed upon "at the (same) time" in Special Relativity for distant events.

It is just as valid to say that the explosion took place at the same time the car was invented. It is just a question of the observer's frame of reference (that's why it is called "Relativity").

The only thing that is non negotiable here is that there is a causal link between the space-time event of the nova explosion and the the space-time event of the arrival of the light emitted during the explosion on earth. There is no observer that can break this causality. But there is even a frame of reference that puts these two events at the same spot in space and time!

For the more mathematically minded: Time and space distances depend on the observer. What is fixed is the space-time distance D, namely:

  D = sqrt( (x2-x1)^2 + (y2-y1)^2 + (z2-z1)^2 -c^2*(t2-t1)^2 )

which happens to be zero for causally linked events.

In Germany, clauses in contracts that come as a surprise and are not prominently displayed are routinely rejected by courts.

Since your friend was not aware of the extra costs in the "contract", I assume the clause with regards to the costs was not very prominently placed on the page. Also, you can not expect costs on pages that state "free", "at no costs", "opensource" and the like.

Therefore if I were your friend:

1. check if the costly clause was not prominently displayed and disguised by other words like "freeware" "at no costs" etc. and if this is the case:

2. make a screen shot of the page. Print it out, date and sign it.

3. reject the first bill that comes in by a letter with proven delivery ("Einschreiben mit Rueckschein"). In the letter, state that the cost clause came as a surprise and that you therefore do not accept the contract. To be on the safe side, also cancel the Contract at the same time (use the words ("Hiermit widerrufe und kuendige ich ausserdem vorsorglich...").

4. sit back and ignore all further bills and communication from that company or their lawyer and money collector. Don't get nervous if they try to scare you and use big words. Ignore them, you already told them all you had to tell them.

5. once eventually a court signed bill ("Gerichtlicher Mahnbescheid") arrives, you MUST reply to the court to reject this bill! Do not ignore this!

6. see if the company dares to go to court after this. I bet they will not as they will very very likely loose if the cost clause was not obvious.

Good luck!